Every time the class teacher walks past the window, the two boys pretend _________ closely.

We ___ for a picnic with you last weekend, but we were too busy with our reports. [ ]

The look on his face suggested that he just happened _______ the secret and _______ he himself was very shocked, too.

_________ water to grow is well-known.

The situation in the country is ________， yet we are still concerned about its future.