Modals of Possibility

Does anyone know where Chris works? I'm not sure, he _____ work in London. (should / might / may)

I feel very tired. I ____ be getting a cold. (should / could / might / may)

You played tennis for four hours straight in the sun. You ____ be thirsty! ( may / could / might / must)

Surely she ______ know about the secret holiday we have planned. We've told nobody! (can't / might / will )