Even if the problem has been encountered before, it is reasonable to suppose that
the person who understands the bas is for the answer is more likely than the one
who does not to give the correct answer.
When using the alternate-choice item form, the item writer is free to pose
questions that admit only two good alternative responses. Here are some
examples:
I. The density of ice is (I) greater (2) less than that of water.
2. A point on the surface of the Earth moves toward the (I) east (2) west as
the Earth turns.
3. The average size of farms in the United States has (I) increased (2)
decreased during this century.
Often, as in these examples, there is only one plausible alternative to the key
word or phrase in the proposition.