Which sentence below is a compound-complex sentence? a. jenny hid the hen, and benny tried (unsuccessfully) to hide the cow. c. i walked to the store to buy some milk. b. the cat lived in the backyard, but the dog, who knew he was superior, lived inside the house. d. it makes me happy that you love me.

The sentence that is a compound-complex sentence is B.  the cat lived in the backyard, but the dog, who knew he was superior, lived inside the house.

Explanation: A compound-complex sentence is a sentence made up of a compound sentence and at least one complex sentence. While a compound sentence includes two independent clauses joined by a coordinating conjunction, a complex sentence includes an independent clause and a dependent clause which is introduced by a subordinating conjunction. B. is a compound-complex sentence because it is made up of a compound sentence, that is to say two independent clauses ("The cat lived in the backyard" and "The dog, who knew he was superior, lived inside the house") and a complex sentence, that is to say an independent clause ("The dog lived inside the house") and a dependent clause ("who knew he was superior").

you need to pay about 1000$ to get out of a airport.

sentence lenght varies according to word choice.you select which word to use and that will require to use other expressions that collocate with the word chosen.sentence length will vary   according to the choice of words you make to express your ideas.