A:was seen beg
B:were seen beg
C:were seen begging
D:was seen begging
Mr Jackson hasn't decided this weekend.
下列现象中,没有发生化学变化的是( )
亚洲河流呈放射状向四周分流的原因是
8 O
氧
16.00
9 F
氟
19.00
10 Ne
____ 20.18