In the following passage some of the words have been deleted. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.

One afternoon, a dozen Arizona State University students (1)______ to spend the morning cutting cardboard, taping fans and assembling filters in an effort to (2)_____ 125 portable air purifiers for local schools. That (3)_______ morning, staff members at a homeless shelter in Los Angeles were setting (4)_______ 20 homemade purifiers of their own, while in Brookline, Massachusetts, another DIY air purifier was whirring quietly in the back of a day care (5)______ as children played.