In which sentence is the underlined phrase an adjective clause? a. a male platypus can eject venom when another animal disturbs it. b. when explorers first sketched the platypus, scientists thought the sketches were a hoax. c. the platypus, which is a mammal, has a bill like a duck and feet like an otter.

C. The platypus, which is a mammal, has a bill like a duck and feet like an otter.

"which is a mammal" is an adjective clause. An adjective clause is used to describe a noun and usually begins with one of these words: that, when, where, who, whom, whose, which, and why. In this sentence, the adjective clause begins with "which" and describes the platypus, which is a noun.

synonymous.

he was ashamed of himself