Concept:Understand the exact meaning of the underlined word and then choose the closest synonym from the given options.
Explanation:The word "clandestine" means something kept secret or done in a hidden, sneaky manner.
This kind of action is usually concealed because it may be illegal or improper.
In the sentence, "clandestine deals" clearly refers to deals that are carried out in a secretive way.
Among the options, "secret" most closely matches this meaning.
"Exclusive" means restricted to certain people, "unimportant" means trivial, and "doubtful" means uncertain.
None of these other words convey the idea of being hidden or concealed.
Therefore, "secret" is the word nearest in meaning to "clandestine" in this context.
Answer:A. secret