See 6
(to) infinitive/-ing forms pp. GRS-
GR6
10.6.15 Put the verbs in brackets into the correct form.
Check in the Grammar Reference Section.

...
1 You should avoid (drive) your car when there
is a flood.
2 We need (buy) food and water before we leave
the city.
3 The residents were looking forward to (get)
back to their normal lives again after the huge tropical storm.
4 Let's (leave) the house now before it's too late!
5 The government spent lots of money on
(repair) the damage from the earthquake.
6 The emergency services are having difficulty ..
(rescue) all of the survivors.
..​

1. You should avoid driving your car when there is a flood.
Explanation: In this sentence, the verb "avoid" is followed by the gerund form (-ing form) of the verb "drive." Gerunds are used after certain verbs, such as "enjoy," "avoid," and "dislike."

2. We need to buy food and water before we leave the city.
Explanation: In this sentence, the verb "need" is followed by the infinitive form ("to" + base form) of the verb "buy." Infinitives are used after verbs like "need," "want," and "have."

3. The residents were looking forward to getting back to their normal lives again after the huge tropical storm.
Explanation: In this sentence, the verb "looking forward to" is followed by the gerund form of the verb "get." Gerunds are used after certain expressions, such as "look forward to," "be accustomed to," and "be used to."

4. Let's leave the house now before it's too late!
Explanation: In this sentence, the verb "let's" is followed by the base form of the verb "leave." The base form is used after the verb "let" to give a command or suggestion.

5. The government spent lots of money on repairing the damage from the earthquake.
Explanation: In this sentence, the verb "spent" is followed by the gerund form of the verb "repair." Gerunds are used after certain verbs, such as "spend," "waste," and "enjoy."

6. The emergency services are having difficulty rescuing all of the survivors.
Explanation: In this sentence, the verb "having difficulty" is followed by the gerund form of the verb "rescue." Gerunds are used after certain expressions, such as "have difficulty," "have a hard time," and "have no trouble."

To summarize, in these sentences the verbs are used in different forms: gerund (-ing form), infinitive (to + base form), and base form. The choice of form depends on the verb used before or after and the specific grammar rule associated with that verb.