Since there are no further instructions and I was not able to find this question online, I will take it that we are supposed to rewrite the sentence in the past perfect continuous tense.
Answer:
The fox had been trying very hard to get at the grapes.
Explanation:
There are a few "tricks" we can use to not mistake verb tenses. First, every time a verb tense has "perfect" in its name, that means it uses the verb "have" as an auxiliary. If it is a "past perfect", we need to use the past of "have", which is had.
Now, every time a verb tense has "continuous" in its name, that means it uses the auxiliary "be" and the main verb ending in -ing. In the case of past perfect continuous, because we already use the auxiliary "had", the verb "be" needs to be used in its past participle form, "been". Thus, we got:
had + been + verb -ing
Having that in mind, we can change the sentence in the following way:
- The fox tried very hard to get at the grapes. --> The fox had been trying very hard to get at the grapes.
