What kind of rock would most likely be formed if an igneous rock was deep under ground for many years

When the igneous rock is deep underground for many years, it will form into metamorphic rock under extreme pressure and temperature. It could also form into magma when it melts deep beneath the layers of earth or it could form sediments when subjected to weather erosion.

i don't know that i agree with that but what's the question ?

answer: the correct answer for the fill in the blank is rods.

rods are the specialized photoreceptor cells that are present in the retina of human eye. they are responsible for vision in the night time ( also called scotopic vision). they have very low visual acuity and color distinguishing ability.

as they are responsible for vision in night time, therefore they are found predominantly in the nocturnal animals.