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• Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest. example: Entamoeba histolytica.
• Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. Example: Ascaris lumoricoides. 
• Polyembryony is the phenomenon of two or more embryos developing from a single fertilized egg. Due to the embryos resulting from the same egg, the embryos are identical to one another but are genetically diverse from the parents. An example is Fasciola hepatica.
• Reservoir host is the host of an infection in which the infectious agent multiplies and/or develops, and on which the agent depends for survival in nature; the host is essential for the maintenance of the infection during times when the active transmission is not occurring. Examples of the reservoir host include  humans, animals, and the environment
• Biological vectors, such as mosquitoes and ticks may carry pathogens that can multiply within their bodies and be delivered to new hosts, usually by biting.
• So, the correct answer is 'a-v,b-iii,c-i,d-ii,e-iv'.

A fomite is any nonliving object or substance capable of carrying infectious organisms, such as viruses or bacteria, and hence transferring them from one individual to another. Fomites are associated particularly with hospital-acquired infections, as they are possible routes to pass pathogens between patients. Researchers have discovered that smooth (non-porous) surfaces like doorknobs transmit bacteria and viruses better than porous materials like paper money.

Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli. Symptoms include some combination of a productive or a dry cough, chest pain, fever, and trouble breathing. Pneumonia may spread via airborne droplets from a cough or sneeze. Pneumonia is usually caused by infection with viruses or bacteria and less commonly by other microorganisms, certain medications and conditions such as autoimmune diseases.

Lead arsenate is a stomach poison, not a contact poison. DDT, BHC, and Endrin are contact poisons that kill insects upon physical contact.

• Measles is a highly contagious infectious disease caused by the measles virus. Symptoms include fever, often greater than 40 °C, cough, runny nose, and inflamed eyes. Measles is an airborne disease which spreads easily through the coughs and sneezes of infected people.
  
• Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Symptoms include a sore throat and fever. In severe cases, a grey or white patch develops in the throat. Diphtheria is usually spread between people by direct contact or through the air (droplet).
  
• Pertussis, commonly known as a Whooping cough is a highly contagious bacterial disease. Symptoms include a runny nose, fever, and cough. Pertussis is caused by the bacterium Bordetella pertussis. It is an airborne disease which spreads easily through the coughs and sneezes of an infected person.
• Gonorrhoea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. Symptoms include burning with urination, discharge from the penis, or testicular pain. Women may have burning with urination, vaginal discharge, vaginal bleeding between periods, or pelvic pain. Hence, it is not transmitted by droplets.

The assertion is true because Taenia (tapeworm) infection is transmitted through undercooked pork containing larvae. The reason is false because the larval stage found in pork is the cysticercus (bladder worm), not the hexacanth (oncosphere), which is the stage found in the egg.

• Droplet infection is an infection transmitted from one individual to another by droplets of moisture expelled from the upper respiratory tract through sneezing or coughing.
• Pneumonia is an inflammation of the parenchyma of the lungs. It is caused by the bacterium Streptococcus pneumoniae.
• Symptoms include a cough with phlegm or pus, fever, chills and difficulty breathing.
• The bacteria that are commonly found in the nose or throat, can infect the lungs if they are inhaled. They may also spread via airborne droplets from a cough or sneeze.
• So, the correct answer is '.Pneumonia ,Streptococcus pnemoniae,Droplet infection'.

Vectors are the organisms, which carries the infectious agents from sick person to another healthy person. For example, mosquito carries malarial parasite from infected person to healthy person. Therefore, option A is correct.

Wuchereria bancrofti is a human parasitic roundworm that is the major cause of lymphatic filariasis. W. bancrofti carries out its lifecycle in two hosts. Humans serve as the definitive host and mosquitos as the intermediate host or vector. The microfilariae are transferred into a vector i.e., female Culex mosquito. Hence, female Culex act as a vector of Wuchereria bancrofti.