2 . Given the breadth of her research, her ______ knowledge on the topic is evident in every chapter of her book.

A．superficial

B．intensive

C．explosive

D．extensive

3 . 选词填空

A. extensive

B. express

C. engage

D. literacy

E. harmony

1. In order to ________ his gratitude, he wrote “I’m much obliged to you for helping us!” at the beginning of the letter.
2. To investigate how ________ levels differed between boys and girls in the U.S., the team studied data collected over three decades in the National Assessment of Educational Progress.
3. According to Guan Zhengwen, the director of Letters Alive, it is this kind of humanity behind every letter that strikes a ________ with the audience.
4. Scientists discovered Zealandia all the way back in 1995, then started ________ research on the area using underwater and satellite mapping technology.

4 . Though Sam's music player didn't work well, he was ________ to throw it away.

A．reluctant

B．steep

C．extensive