If people eat natural poisons by mistake, they ________ go to hospital without delay.
George has arrived, but I did not know he ______ until yesterday.
It ______ six years since they last saw each other.
Look at these clouds. ______.
-- Could you give these books to Mr. Mackintosh?-- Certainly, ______ him about something else in any case, so it won't be any bother.
Lu Xun ______ a lot of novels.