【2020最新整理国开(电大)人文英语1-3896网上形考机考题库】They _____________ some social work at the weekends.

【2020最新整理国开(电大)人文英语1-3896网上形考机考题库】They _____________ some social work at the weekends.
选择一项：
A. do
B. does
C. did