Correct answer: A
Knowledge of type words:
A. preferable /ˈprefərəbəl/ (a): better
B. prefer /prɪˈfɜːr/ (v): like
C. preference /ˈprefərəns/ (n): preference, preference
D. preference /prefərˈenʃəl/ (a): preference
After the verb to be we need an adjective. From there, we eliminate B, C
They seem to feel that the danger of the traffic is (27)_______ to the risk of having their conversation be overheard.
They seem to feel that the danger of traffic is better than the risk of their conversation being overheard.