WORKSHEET
3. Past Perfect Continuous
The fox tried very hard to get at the grapes.

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.

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.

you did not put the article. so i cannot answer the question.