Convert compound sentence to simple sentence:
He is rich, yet he is unhappy.

a) He is rich but also unhappy.
b) He is rich and unhappy.
c) Even though he is rich he is unhappy.
d) Despite being rich he is unhappy

Hint: In order to convert the compound sentence into a simple sentence, you need to convert one of the verbs into a continuous verb.

Complete answer:
 A simple sentence is a sentence containing only one clause, i.e. one subject and one predicate. A compound sentence with more than one subject and predicate. They are usually joined together using conjunction.

Compound sentences contain two clauses. In order to convert a compound sentence into a simple one, all we have to do is convert the number of clauses into one.

Now, let’s look at the available options:

>He is rich but also unhappy - This sentence is still a compound sentence. There are two clauses which are joined together by a conjunction. This is not the required answer. So, this is an incorrect option.
>He is rich and unhappy - This sentence is also a compound sentence. This contains conjunction which joins the two clauses together. This is not the required answer. So, this is an incorrect option.
>Even though he is rich, he is unhappy - This sentence contains two clauses, too and it contains conjunction. This is also not the required answer. So, this option, too, is incorrect.
>Despite being rich, he is unhappy - In this sentence, there is only one clause. There is no conjunction, and there is an ‘-ing’ verb. This is a simple sentence. So, this is the correct answer.

Thus the correct option is ‘D’

Note: It is important to remove the conjunctions from compound sentences in order to convert them into simple sentences. This will help to remove one clause from the sentence. Then, scan through the options to find the sentence with one clause, which will be the correct option.