Concept:The expression “can’t be too careful” is an idiom that stresses the need for extreme caution.
Explanation:This phrase does not mean that a person is unable to be careful.
Instead, it means that one should take no risks at all.
A person should always be watchful and prudent in a situation.
When applied to a relationship with someone, it suggests that one must remain guarded and vigilant.
Therefore, the speaker is advising that he “has to be very careful in his relationship with Wang.”
Answer:C. has to be very careful in his relationship with Wang.