a student is observing a rock. which of the follwoinf is an observation

Question

1. the rock is 55g in mass
2. the rock is over billions of years old

Answer 1

i put 2 on my test
can u explain why its 2.

Answer 2

You wouldn't know the mass of the rock by a simple observation. You'd have to weigh it.

Answer 3

so using an instrument to extend the power of an observation isnt itself an observation?