English Grammar and Usage

Here, the word 'year' is preceded by a numerical figure (five) but succeeded by a noun (plan). In this case, the word 'year' will be written in singular. The phrase will be written as 'five-year plan'.

(senior to). The adjectives of comparative degree like Senior, Junior, Inferior, Superior are always followed by ‘to’ instead of ‘than’.

(to). With the word exception we use preposition ''to''.      

(would have). Past indefinite tense is being used. 

(leave blank). No determiner is needed to begin the sentence. 

(Although). Right conjunction used; although expressing a concession.

Present tense has to be used after the line 'since he left the presidency years ago...'. Hence, option 4 is the correct answer.

'Abridge' means to shorten, condense, or reduce something in length or scope while keeping its essential meaning - like an abridged version of a book that is shorter than the original. Among the options, 'Reduce' is the only word that captures this meaning of making something shorter or smaller.

(geometric designs): Rule of maintenance of parallelism

Correct conjunction and auxiliary should be used, since the subject is singular. The quality of soil is a restrictive clause, so 'that is' should be used.

You excel at an activity. ('in' is used with a subject.)

(Both): Conjunction ''and'' is preceded by ''both'' and ''both'' is used for two people or things.

Knowhow (or know-how) means practical knowledge, expertise, or skill in doing something. 'Technical knowhow' is a common collocation referring to hands-on technical knowledge and experience.

(Tornadoes almost never occur). Correct word order

(from). Correct preposition because you always take something from somewhere.