One way for students to prevent H7N9 flu virus is to openthe windows of the classroom to allow the air to ________.

These suitcases are too heavy for me to move—Here, I’ll give you a hand _______ them

We would like you_______ and we look forward_______ you.

There is a popular view in cities, strangers are less likely to help an elderly person.

Mary, let’s go to the bookshop this weekend. Will you be ______?—Sorry, but I’m going to visit my uncle in the countryside.[ ]