12.—Most of my friends do the shopping online,—That’s really a good idea. Prices of goods _______ online can be lower than store prices.
______, the concert began.
---- You shouldn’t have gone there alone last night. ---- But I ______, because Xiao Wang went there, too.
---- There is a lot of smoke coming out of the teaching-building there. ---- Really? It _____ be a fire, most probably.
If you don’t wait _______ the red light, you will be punished by the policeman.
________ doesn’t seem to have been much difficulty in solving the problem.