Though the sentry and the messenger are minor characters in the play, what important function do they fulfill?
a. they criticize the king's orders offstage.
b. they carry out the king's orders while offstage.
c. they inform major characters of events that happen offstage.
d. they commit acts of dramatic violence offstage.

The correct sentence pattern is 1. s-lv-pa.

Explanation: The sentence provided ("Relaxing under a shady tree is very pleasant") is made up of a subject (s), a linking verb (lv) and a predicative adjective (pa). "Relaxing under a shady tree", which is a gerundial phrase, is the subject and "is" is the linking verb because it does not refer to an action but it actually establishes a relationship between the subject of the sentence and what it comes after the verb: the predicative adjective ("(very) pleasant". A predicative adjective presents or describes a characteristic of the subject and it always follows a linking verb.