You have received a birthday gift from a friend of yours. Now write him/her a note, acknowledging the gift and expressing your thanks.
Marks will be awarded for content, organization, grammar and appropriateness.

A. was similar to the sound location system of the bats
B. led to a product that sent out sound waves of about 20,000 cycles per second
C. was experimented on a submarine
D. turned out to be a failure

A. a series of volcanic eruptions
B. the collapse of rock formations in the Colorado Plateau
C. a succession of floods from the Hualapai River and what is now the Colorado River
D. the Earth’s internal pressure lifting the Colorado Plateau region