Sending signals at optical wavelengths might be a viable ...

[jazziefee]

Sending signals at optical wavelengths might be a viable alternative to radio wavelengths
 
  A) only between civilizations around solar-type stars whose eyes have evolved to see such radiation
  B) over relatively short distances where absorption by interstellar matter would not be a problem
  C) as long as the light transmitted is a different color than the light given off by the parent star
  D) over all distances as long as the intensity of the signal is strong enough

Question 2

The images formed by concave lenses
 
  A) are always virtual.
  B) could be real or virtual, but always real when the object is placed at the focal point.
  C) could be real or virtual; it depends on whether the object distance is smaller or greater than the focal length.
  D) are always real.

[jonathanballen97]

Answer to Question 1

B

Answer to Question 2

A

[jazziefee]

TY

[jonathanballen97]

You're welcome