Anyone else single...just me ight...

Can someone me with questions 15 to 17 plz.

Light waves can move through , but they travel fastest when they move through a(n) .

Polar bears give birth and hunt on sea ice. which of the following would polar bears survive during the melting of arctic ice? growing another layer of fur during summer migrate inland to search for different food sources staying put until the ice refreezes sticking to the usual diet of seals