What units are used when describing the length of time that the universe has been expanding? multiple choice a billions of years b millions of years c light years d light year kilometers e decades

I believe the answer is A) Billions of years since the universe is 13.8 Billion years old

A

Step-by-step explanation:

Assuming this is a "multiple choice question" where 1 answer is right

We are looking for a unit of "time", so option C and D are eliminated since both are units of "distance".

Looking at the other choices,

Decades mean 10 years and to describe the age of universe with this "small" number is inconvenient. So this is not right.

Millions of years is a big number, but comparing to the expanding time of the universe, it is rather small. We now know that after the Big Bang, around 5 or 6 billion years it has gone since the universe is expanding. So millions of years is small.

Billions of years will be the correct unit since it has been known that the universe has been expanding for the past 5 to 6 billion years.

Answer choice A is right.

the 3rd option is right

step-by-step explanation:

step-by-step explanation: s