Explanations:The correct answer to the question "Last year, an aeroplane ..... into the mountain" is "crashed." This sentence requires the use of the past simple tense to describe a completed action that occurred in the past. The past simple tense is used to talk about actions that were completed at a specific time in the past, and it is often used with time expressions such as "last year," "yesterday," or "in 2020."
Irregular verbs are verbs that do not follow the regular pattern of adding "-ed" to form the past simple and past participle forms. Instead, they have unique forms that must be memorized. For example, the verb "crash" is an irregular verb, and its past simple form is "crashed." Other examples of irregular verbs include "go" (went), "eat" (ate), and "run" (ran).
It is important to note that the past simple tense is formed using the base form of the verb for regular verbs, but for irregular verbs, the past simple form is often different from the base form. In this case, "crashed" is the correct form to use because it is the past simple form of the irregular verb "crash."
The other options provided in the question are incorrect for the following reasons:
Option A, "crash," is the base form of the verb and does not indicate past tense. The sentence requires the past simple form to describe a completed action in the past.
Option B, "crashes," is the present simple form of the verb, which does not match the time reference "last year" in the sentence. The sentence requires the past simple form to describe a completed action in the past.
Option D, "were crashing," is in the past continuous tense, which is used to describe an ongoing action in the past. The sentence requires the past simple form to describe a completed action in the past.
Understanding the correct use of verb tenses, especially for irregular verbs, is crucial for constructing grammatically correct sentences and accurately conveying the timing of actions. In this case, the past simple form "crashed" is the appropriate choice to describe the completed action of the aeroplane crashing into the mountain last year.