Polar bears’ hair
a. is transparent
b. is hollow
c. keeps them from getting wet
d. all of the above

D) all of the above

all of the following attributes are true:

a. is transparent

b. is hollow

c. keeps them from getting wet

lunar landing mission. apollo 11 was the first manned mission to land on the moon. the first steps by humans on another planetary body were taken by neil armstrong and buzz aldrin on july 20, 1969. the astronauts also returned to earth the first samples from another planetary body.

explanation:

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.