The correct answer is C. Speak.
Indolence is the state of being lazy or idle, while work is the activity of doing something that requires physical or mental effort. Taciturn is the quality of being habitually silent or reserved in speech.
In the same way that indolence is the opposite of work, taciturn is the opposite of speak. A taciturn person is not very talkative, while a person who is not taciturn is talkative.
The other options are not correct because they do not have the same relationship to the words in the question as indolence and work do.
A. Cheat is not the opposite of work. Cheating is the act of breaking the rules in order to gain an unfair advantage, while work is the activity of doing something that requires physical or mental effort.
B. Act is not the opposite of taciturn. Acting is the performance of a play or other dramatic work, while being taciturn is being habitually silent or reserved in speech.
D. Observe is not the opposite of indolence. Observing is the act of watching something carefully, while being indolent is being lazy or idle.
