--When did you become a volunteer for the elderly?-- Two years ago. I        this group since then.
#42442
A
joined
B
took part in
C
have joined
D
have been in
推荐题目
John       to London to watch the Olympic Games next week.
#40658
A
flies
B
flew
C
will fly
D
has flown
Since we ________ our homework now. Let’s have a rest. 
#41543
A
do
B
are doing
C
will do
D
have done
The train _______. Please get ready to get off.
#42532
A
arrives
B
arrived
C
is arriving
D
to arrive