People ______always be careful with fire， or it can be dangerous.

Every time when something ____ me, I turn on the radio and listen to music.

There will be a stamp show in the museum ______ we visited last week. [ ]

When and where shall we meet tomorrow? —Let’s _______ it 3:00 p. m. at my home.

If he takes on this work, he will have no choice but ______ an even greater challenge.＿