Which sentence is written correctly?
a. our group fared poorly; none of the judges seemed to pay attention to us.
b. for better or worse; we have decided to put the old house up for sale.
c. it is nearly 8 p. m., so; we really need to be going soon.
d. mark's car is big; but it is full of junk.

The answer is A.

Explanation:

Semicolon( ; ) is a punctuation mark used to separate two independent clauses. Independent clauses are the ones that carry the meaning on their own and can function as a sentence. Clauses separated by a semicolon are still in the same sentence, that's why the clause after the semicolon does not start with a capital letter (of course unless it starts with a proper noun). Besides being independent, these clauses also need to be logically and semantically connected, stating a similar thing or complementing each other. Semicolon functions as a link between the two clauses, so there is no need for putting conjunctions such as and, so, therefore etc. Having this in mind, we see that A is correct answer.

In answer B, for better or for worse is a phrase ( it lacks a verb) not a clause.

In answer C there is a conjunction SO. We don't use both semicolon and conjunctions.

In answer D, both clauses are independent, but their meanings are opposing. We use semicolon only if the meanings are similar (e.g. Mark's car is big; the family will enjoy the driving).

the police rob enrique and other migrants and they deport them back

i think there should be answer choices