Idioms and Phrases - Verbal and Reasoning

In the following questions four alternatives are given for the idiom/phraseitalicised and underlinedin the sentence. Choose the alternative which best expresses the meaning of idiom/phrase.
Q1:

It is no longer easy to strike gold in Shakespeare's research since much work has already been done on him.

A Hit a golden spot

B Come across gold

C Come across the word "gold"

D Uncover or find a valuable line of argument or information

ANS:D - Uncover or find a valuable line of argument or information

No answer description is available.