A compound sentence can be thought as two or more simple sentences joined by a compound or an appropriate mark of punctuation.
A conjunction is the part of speech that serves to connect words, phrases, clauses, or sentences. Some common conjunctions are and, but, or, yet, for, nor, so, then, than, since, and some more.
Punctuation Marks are colons, semicolons, comma, exclamation mark, question mark and also more.
In the examples the correct answer would be:
b) We are going to an apple orchard today; then we will make different desserts with all the apples.
Repetition of more than two conjunctions in a sentence, in this case the use of semicolon, the conjunction then and the conjunction and do not match English grammar rules. When two complete sentences are joined by a conjunction, we should generally place a comma before a conjunction but not exceed that amount.