Hubble's expansion law states
a.) the distance of a galaxy is proportional to its recessional speed
b.) the universe is expanding
c.) galaxies and stars are making a redshift
d.) the distance of a galaxy divided by its recessional speed determines its redshift.

i'm not sure if it's a or d

The correct option is Option A.

Explanation:

Hubble's law states that the distance to a galaxy is proportional to its recessional velocity.

Mathematically,

where,

v = recessional velocity of galaxy

= Hubble constant

d = distance to galaxy

The Hubble's constant is the proportionality constant present between the recessional velocity of galaxies and their distance.

This law does not say anything about red shift.

Hence, the correct answer is Option A.

d

explanation:

v=uf/(u-f)

= 5.10/(5-10) convex lens has positive focal length

=50/-5

=-10 cm (formed at other side)