In this task, you are given a premise, a hypothesis, and an update. The premise sentence describes a real-world situation and is always assumed to be true. The hypothesis sentence describes an assumption or inference that you might make about that situation having read the premise. The update provides additional information about the situation that might weaken or strengthen the hypothesis. A weakener is a statement that weakens the hypothesis, that is, it makes you much less likely to believe the hypothesis is true. A strengthener is a statement that strengthens the hypothesis, that is, it makes you much more likely to believe the hypothesis is true. Your task is to answer with 'strengthener' or 'weakener' if the update strengthens or weakens the hypothesis, respectively.

Premise: A gray dog is in grass.
Hypothesis: A dog is sitting in the grass
Update: The dog's tail cannot be seen because the dog's bottom is on the ground.
strengthener

Premise: One man is singing into a microphone and another musician is playing the guitar while standing next to each other.
Hypothesis: The man played the guitar very well.
Update: The other members of the band stop playing and let the guitar player take over as the crowd cheers.
strengthener

Premise: Two children, one in a yellow shirt and the other in red rain boots, swing on the swings at a playground.
Hypothesis: There is water on the ground.
Update: The sky is very dark and cloudy.

strengthener