Answer:
A) Alive, the elephant was worth at least a hundred pounds; dead, he would only be worth the value of his tusks, five pounds, possibly.
Step-by-step explanation:
Semicolons are used to indicate a pause longer than that of a comma, but shorter thant that of a period.
When you have two independent clauses whose ideas are closely related, the semicolin is commonly use to link both clauses
Let's see every sentence.
B) Alive, the elephant was worth at least a hundred pounds. Dead; he would only be worth the value of his tusks, five pounds, possibly.
The pause after "Dead" should be equal as the pause after Alive. The comma after Alive is correctly used because that is a very short pause. Thus, after Dead there should be a comma, not a semicolon.
C) Alive, the elephant was worth at least a hundred pounds. Dead, he would only be worth the value of his tusks; five pounds, possibly.
What comes after "tusks" is a further detail (explanation) about what the value of the tusks could be; thus, there should be a comma not a semicolon.
D) Alive, the elephant was worth at least a hundred pounds and; dead, he would only be worth the value of his tusks, five pounds, possibly.
Using a semicolon after "and" is a msitake because you should not add a pause after the conjunction.
The first sentence, A) Alive, the elephant was worth at least a hundred pounds; dead, he would only be worth the value of his tusks, five pounds, possibly, correctly implements the semicolon after the first clause, to link with the second clause, with an intermediate pause.