Two independent clauses may be joined by

using a comma with a conjunctive adverb
using a semicolon between the clauses without a conjunction
using a semicolon before a conjunctive adverb
using a semicolon before a list of items relating to the subject
using a comma before the conjunctions and, but, or, for, nor, so, and yet

The correct answer is using a comma before the conjunctions and, but, or, for, nor, so, and yet.

Explanation:

Independent clauses, defined as phrases that can stand alone as a complete thought, are commonly joined together in compound sentences. These compound sentences are commonly defined as two or more independent clauses joined together with coordinating conjunctions such and, but, or, for, nor, so, and yet, or a semi-colon.

Bearing the above in mind, it could be said that from the options provided the choice that better suit the statement "Two independent clauses may be joined by " is using a comma before the conjunctions and, but, or, for, nor, so, and yet

c -invasion by the moroccans.