Which of the following sentences contains a compound subject?
a. my grandparents moved here from austria.

b. their friends and relatives from austria visit often.

c. they speak both english and german.

d. austria is a very interesting country to visit.

The sentence that contains a compound subject is B. Their friends and relatives from Austria visit often.

Explanation:

The subject of a sentence is the person, thing or idea that carries out the action defined in the predicate. When the sentence has two or more subjects, that subject is called compound subject. In a compound subject, the individual subjects are joined by a coordinating conjunction, such as and, or, etc. In this case, the individual subjects that form the compound one are their friends and relatives (from Austria.)

comfortable

explanation:

one type of the adjectives is predicate adjective. a predicate adjective is an adjective which follows a linking verb and modifies or refers back to the main subject of that linking verb.

it usually is used just before the noun it modies.

here in this example:

'penguins seem comfortable in the coolest habitats', comfortable is the predicate adjective which follows the linking verb 'seem' and modifies the noun.