问题
选择题
I found John _____ the desk, _____ his homework carefully.
A．seated at; to do
B．sitting at; doing
C．sat at; does
D．taking his seat at; to do
答案
答案：B
搜题请搜索小程序“爱下问搜题”
I found John _____ the desk, _____ his homework carefully.
A．seated at; to do
B．sitting at; doing
C．sat at; does
D．taking his seat at; to do
答案：B
，该粒子属于____（填“原子”“阳离子”或“阴离子”），其符号为____。 