You’d better wear a pair of comfortable trainers when ________a long walk.
—I’m sorry, sir. I’ve made lots of mistakes in the monthly exam.— Never mind. ___________, the exam is a bit difficult.
—What can you see _________ the bridge, Millie?—Oh, an elephant is standing over there. Let’s go and see it.
— Must I turn off the gas after cooking?— Of course. You can never be________ careful with that.
---Can you describe what Mr. Green's daughter is like?--- Oh, she has the very_______ of Mr. Green. I'm sure you can know her at the first sight.
We can have ________ bluer sky if we create _________less polluted world.