Question

Early airships such as zeppelins were filled with hydrogen. Today’s blimps use helium instead. Which correctly combines the two sentences using a compound sentence? Today’s blimps use helium instead, but early airships such as zeppelins were filled with hydrogen. Early airships such as zeppelins were filled with hydrogen, but today’s blimps use helium instead. Early airships such as zeppelins were filled with hydrogen: however, today’s blimps use helium instead

Answer 1

To combine these sentences together to flow neatly and be grammatically correct you could say: Early airships such as zeppelins were filled with hydrogen, but today's blimps use helium instead. This is the correct answer out of your choices.

Your answer is: Early airships such as zeppelins were filled with hydrogen, but today's blimps use helium instead. 

Have an amazing day and stay hopeful!

Answer 2

The correct answer is "Early airships such as zeppelins were filled with hydrogen, but today’s blimps use helium instead".

Explanation:

A compound sentence refers to a type of sentence that includes two or more ideas of the same importance link one coordinating conjunction such as and, or, but, so. This implies in the case of combining two or more sentence to create a compound sentence any of the conjunctions previously mention need to be included. Besides this, because the sentences combined are "Early airships such as zeppelins were filled with hydrogen" and "Today’s blimps use helium instead", the most correct way is to include first the sentence "Early airships.." and then the sentence "Today's blimps use helium instead" as the word "instead" makes reference to the first sentence.

This implies, the correct way of combining this sentence is "Early airships such as zeppelins were filled with hydrogen, but today’s blimps use helium instead", because in this the correct order of the sentences have been preserved and also the conjunction "but" has been added which creates a compound sentence and also shows the contrast between the materials used in zeppelins and blimps.