What is similar about the discoveries of Neptune and Pluto?

(1 point)
They were both identified as planets by virtue of their movement in the sky.
They were discovered within 10 years of each other, so roughly at the same time.
They were both recognized to be planets because of objects orbiting them.
They were discovered as planets by use of the sextant.

They were both identified as planets by virtue of their movement in the sky.