Chapter 4 — Verb tenses and forms

The essentials in four points:

• Since / for + duration → present perfect: Since 1998, the observatory has collected…
• Past perfect for an action prior to another past action: By the time they arrived, the climbers had reached the shelter.
• Every sentence needs a conjugated verb: a lone -ing form is never enough.
• Some verbs require the gerund (postpone, avoid, enjoy) or the infinitive (hope, decide, agree).

The ITP does not test the stylistic nuance of tenses but their obligatory markers: certain words in the sentence mechanically impose a verb form. Learning these triggers earns immediate points.

1. Tense triggers. Since + starting point / for + duration / so far / over the past decade → present perfect. By the time + past → past perfect in the other clause. Ago, in 1998, last year → past simple.
✔ Since 1998, the observatory has collected data.
✔ By the time the team arrived, the climbers had reached the shelter.

2. The missing main verb. A whole sentence built around being, to be or a relative clause has no conjugated verb: a classic sentence-completion question. First check whether the sentence already has its main verb.
✔ The results of the experiment were inconclusive. (the only conjugated option)

3. Infinitive or gerund after the verb. hope, decide, plan, refuse, agree + to + base; postpone, avoid, enjoy, finish, consider, suggest + -ing.

4. The subjunctive after verbs of demand. require, recommend, suggest, insist, demand + that → base form, no -s, no will: The guide requires that every citation follow a standard format.