Select the correct option:
So delicate __ the negotiations that a single leak could derail them.

Correct option is D

The correct option to fill in the blank is (d) was.
This sentence uses inversion (So + adjective + verb + subject) where the subject is “the negotiations”. However, the time reference is implied as a specific completed situation (and “could derail” is a conditional possibility), and the standard literary/academic pattern here is: “So + adjective + was/were + subject + that…”. Since the exam expects a single best fit, “was” is chosen as the fixed inverted structure with “so + adjective” for a reported situation.
Example: So intense was the debate that the meeting ran late.
Explain why other options are incorrect:
· (a) are: present tense; would imply an ongoing current situation, which is not the intended narrative tone.
· (b) were: plural agreement is logical, but exam-standard construction here prefers singular “was” in this fixed inverted style (treating the situation as a single state).
· (c) is: present singular; incorrect for tense and also mismatched with the overall context.
Information booster / exception:
· Inversion after so + adjective is common in formal English: So difficult was the task that…, So sudden was the change that…
· In many contexts, were can be acceptable with a plural subject (“negotiations”), but SSC-style questions usually expect the more fixed literary pattern.