Q: Given the sentence "A little girl sitting on bleachers." is it true that "A little girl is sitting down."?
A: Sitting on a bleachers can be only done while sitting down.
The answer is yes.

Q: Premise: "A group of people on a bicycle trip taking a break on a street corner."
Hypothesis: "A group of people take a brek from riding their bikes."
Do we know that the hypothesis entailed by the premise?
A: From riding bikes tells from what the people are taking a break.
The answer is yes.

Q: Premise: "Man with beard."
Hypothesis: "Sunglasses and an aviation jacket standing next to a round flotation device."
Do we know that the hypothesis entailed by the premise?
A: The aviator poses for a picture with the life preserver that saved him.
The answer is it is not possible to tell.

Q: Premise: "A dog in the water while three individuals walk across a rocky footbridge."
Hypothesis: "Someone from the group threw a stick into the water and the dog is chasing it."
Do we know that the hypothesis entailed by the premise?
A:
One of the individuals would not have necessarily thrown a stick. The dog would not necessarily be chasing a stick.
The answer is it is not possible to tell.