Can someone help me asap this is due at 2 50

Which is not true about oxygen-17 and oxygen-18?

In a stagnant pool of water, a crayfish may spend much of its time lying with one side of its carapace near the surface of the water. in this position, it will move the walking legs on that side in a rhythmic back-and-forth motion. explain the likely function of this behavior.

For which pair of objects would adding the same a