Answer:
3. have become
Explanation:
A verb is one of the parts of speech in English language. Verbs can be defined as any word that describes an action, occurrence, or state of existence. Some examples of verb are dance, sing, walk, play, run, sit, etc.
When a verb is used in its basic form, it is known as its infinitive while when it is used as an adjective or to form tenses, it is known as its participle.
Basically, the present participle of a verb ends with "ing" such as cooking, calling, singing, dancing etc., while its past participle sometimes ends with "ed" such as ringed, loved, talked, singed, etc.
Also, verbs are used for linking the subject of a sentence to its predicate such as seem, remain, become, etc.
Therefore, the most appropriate option to choose is "have become" because it describes the condition of the subject (computers and smartphones).
Hence, computers and smart phones have become smaller and easier to use for several times.
