With the fast development of computer and Internet technologies, traditional printed books ______ by the growing popularity of online reading of e-books.
#101859
A
are challenged
B
have challenged
C
are being challenged
D
have been challenged
推荐题目
— You look tired.— Yes. I ___ non-stop until 8 o’clock.
#102862
A
had worked
B
work
C
have worked
D
was working
The key you have just got     the front door. 
#102563
A
is used to opening
B
is used to be opened
C
is used to being opened
D
is used to open