Question

the security investigation concluded: \there is nothing in subjects background or character that would make him vulnerable to blackmail, extortion, coercion or duress.\ in this sentence, vulnerable means: not ready to receive to new ideas showing evidence of moral and intellectual advancement susceptible to criticism or persuasion or temptation characterized by directness in manner or speech

Explanation:

In the context of blackmail, extortion, coercion or duress, "vulnerable" means being susceptible to such negative - influence actions. It implies being in a position where one can be easily influenced or pressured.

Answer:

C. susceptible to criticism or persuasion or temptation