Control and Coordination (Class - X)

Tropism means movement in response to stimuli. Plants show movement in response to stimuli. 
Chemotropism is the movement of plants in response to chemicals. It can be away or towards chemicals, e.g. growth of pollen tubes towards ovules in response to some chemical substances that are secreted by ovules to attract pollen tubes.

Ethylene is an inhibitor which causes abscission by destructive effect on auxins. Some fruits will produce ethylene as ripening begins. Apples and pears are examples of fruits that produce ethylene with ripening.

The communication between the central nervous system (brain and spinal cord) and other parts of the body is facilitated by peripheral nervous system consisting of cranial nerves arising from the brain and spinal nerves arising from the spinal cord. Thus, our brain allows us to think and take actions.

Vertebral column - The vertebral column (backbone or spine) is a column consisting of 33 vertebrae. It protects the spinal cord in spinal canal and is not a protective structure of the brain.
Meninges are membranes that envelop the central nervous system (brain and spinal cord). The primary function of Meninges is to protect the central nervous system.
Aqueous humour is a thick watery substance that fills the space between lens and cornea.
Cerebrospinal fluid is a clear body fluid that surrounds the brain. It acts as a cushion for brain and helps in exchange of nutrients between brain and nervous tissues as it flows throughout the inner ventricular system of brain and is absorbed back into the blood stream, rinsing the metabolic wastes from the central nervous system.

Reflex is an action that occurs automatically and involuntarily. Running fast to win a race is a voluntary action. 

The cerebrum is a major part of the brain, controlling emotions, hearing, vision, personality and intelligence. It also controls all the voluntary actions.
The functions of pons include sensory roles in hearing, equilibrium and taste, and in facial sensations such as touch and pain, etc.
Hypothalamus is a part of the brain which is important in regulating internal activities like body temperature and release of hormones.

Therefore, the correct answer is ‘cerebrum’.

Growth of a plant is inhibited by abscisic acid. It functions in many plant-developmental processes, including bud dormancy.

The information acquired at the end of dendritic tip of a nerve cell sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of axon, the electrical impulse sets off the release of some chemicals. These chemicals across the gap start a similar electrical impulse in a dendrite of the next neuron. Therefore, only two types of impulses are involved in processing nerve signal viz. electrical and chemical.
Physical (touch) or mechanical (machines) impulses cannot be involved in the transmission of impulse at the end of axon or throughout the nerve conduction.

Adrenal gland is situated on the top of each kidney. These are endocrine glands that produce a variety of hormones including adrenaline and steroids aldosterone and cortisol. 

Iodine is necessary for the thyroid gland to make thyroxin hormone. Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for the growth. In case iodine is deficient in our diet, there is a possibility that we might suffer from goitre.