I ____ sure we will see a deer.

can + not (contractions)

We ____ walking across the park. (Remember: we is plural or 2 or more)

there + is (contractions)

She ____ not been in Alaska yet. (Remember: she is singular or only one)

past form of the verb "sit"

do + not (contractions)

Birds ____ singing. (Remember: birds is plural or 2 or more)

past for of the verb "run"