Explanations:In English grammar, verbs are used to express actions, occurrences, or states of being. Verbs can change their form to indicate different tenses, which help to specify when the action occurred. The past tense is used to describe actions that happened in the past, and it is crucial to use the correct form of the verb to convey this accurately.
Regular verbs in English typically form their past tense by adding "-ed" to the base form of the verb. For example, the past tense of "walk" is "walked," and the past tense of "talk" is "talked." However, irregular verbs do not follow this pattern and have unique past tense forms. The verb "decide" is an irregular verb, and its past tense form is "decided."
The sentence "They decided to go on a trip last summer" requires the past tense form of the verb "decide" because the action of deciding occurred in the past, as indicated by the phrase "last summer." The correct form to use here is "decided," which is the past tense form of the irregular verb "decide."
It is important to note that the other options provided in the question are incorrect for the following reasons:
Option A, "decide," is the base form of the verb and does not indicate past tense. It would be used in a sentence like "They decide to go on a trip this summer," which describes a present or future action.
Option C, "deciding," is the present participle form of the verb, which is used to describe ongoing actions or as part of the progressive tense. It would be used in a sentence like "They are deciding to go on a trip," which describes an action that is currently happening.
Option D, "decides," is the third-person singular present tense form of the verb. It would be used in a sentence like "He decides to go on a trip," which describes a present action performed by a singular subject.
Understanding the correct use of past tense for both regular and irregular verbs is essential for constructing grammatically correct sentences that accurately convey the timing of actions. In this case, "decided" is the correct form to use because it correctly indicates that the action of deciding occurred in the past.