Answer:
The correct answer is: past perfect progressive.
Step-by-step explanation:
He had also been hoping to link his files to those of other scientists and engineers.
The underlined tense is past perfect progressive. We use this verbal tense to describe an action that started in the past and continued to another moment in the past. This means that the duration of action continues but it stops before some other action in the past. We form this tense with had been + present participle of the main verb.
The sentence above shows us both the cause and effect of an action in the past. At some point in the past, the speaker was hoping to his files to the files of other scientists and engineers, which already have existed.