Answer: beryllium
Explanation: i took the test i got it right!!
may vary depending on the organization.
A concave lens is a lens that has at least one of its surfaces or both surfaces curved inwards. Due to this reason, this lens diverges the light that falls on it and hence is also called a diverging lens. The concave lens is thinner in the middle compared to its edges. These are used in flashlights, binoculars, telescopes, etc.
Please see attached image for reference.
20m away
the dog was 60m away from. you subtract 40m since it is 10m/s x 4 seconds