1. When ---in arctic regions, the Aleuts construct igloos as temporary winter shelters.
(A) travel
(B) to travel
(C) traveling them
(D) traveling
2. Most substances contract when they freeze so that the density of a substance's solid is ---of its liquid.
(A) than the higher density
(B) higher than the density
(C) the density is higher than that
(D) the higher the density
3. The mechanism by which brain cells store memories is ---clearly understood.
(A) none
(B) no
(C) not
(D) nor
4. Desert animals ---a means of retaining moisture in such a hot, dry climate if they are to survive.
(A) need
(B) needing
(C) to need
(D) was needed
5. ---state of Wyoming is also known as the "Equality State" because Wyoming women were the first in the nation to vote.
(A) The
(B) There is a
(C) That the
(D) As the
