Select the opposite of the given word:
Rigid
A) hard
B) Toxic
C) Strong
D) Flexible

Hint: Antonyms are the words that are opposite in meaning to another. The root words for the word 'antonym' are the words 'anti' meaning 'against' or 'opposite' and 'onym' meaning 'name’. For instance: the antonym of ‘hot’ is ‘cold’.

Complete answer:
The meaning of the word rigid is ‘stiff or fixed’. So, as per the question we must find the word which is opposite in meaning to the word rigid.
Option A) hard - is an incorrect answer because the meaning of hard is ‘solid, firm, and rigid; not easily broken, bent, or pierced or rigid or firm’ and this is not antonym of the word rigid. Thus, this is an incorrect answer.
Option B) Toxic - is an incorrect answer because the meaning of toxic is ‘poisonous or dangerous’ and this is not antonym of the word rigid. Thus, this is an incorrect answer.
Option C) Strong - is an incorrect answer because the meaning of strong is ‘having the power to move heavy weights or perform other physically demanding tasks or powerful or muscular’ and this is not antonym of the word rigid. Thus, this is an incorrect answer.
Option D) Flexible - is the correct answer because the meaning of flexible is ‘capable of bending easily without breaking or bendy or not so stiff’ and this is the antonym of the word rigid as they have different meanings or they are opposite in meaning to each other. Thus, this is the correct answer.
Rigid – flexible (Option D)

Hence the correct answer is option ‘D’.

Note:Antonyms are the words that are opposite to each other i.e. antonyms of rigid are flexible and synonyms are the words that are similar in meaning. So, the synonym of the word rigid is hard (Option A is already given in the question). Thus, Option D is the most appropriate answer as compared to the other options.