The answer is the first choice. Both verb tenses are in the past tense and agree with each other.
A computer is a common noun.
Common nouns are things that are just as the name suggests, common. An easy way to remember the difference are proper nouns are nouns you capitalize. States and people's names are two examples of proper nouns. Common noun examples include apple, monkey, and cell phone.
The answer is
Yet.
A coordinated conjuction is a word that joins or coordinates two senteces together, in this case the word yet is conectint he was but a child, and giving meaning to the whole sentece by conecting to he did so much for others, if you read it without the yet, the sentence looses force in the statement.
