Alice help her mother do housework on weekends.A、often B、has to C、have to
—David has made great progress recently.—________, and ________.
Mary with her sisters ________ Chinese in China.
Students should do everything they can ________ their study.
—I don’t know if Dr. White _______ to the party next week?—I think he will come if he ________ free.
Shanghai is _______ one of the two cities.