I’m 1998, scientists discovered that the expansion of the universe has been accelerating what force is causing the phenomena a. dark energy b. hubble’s law c. the doppler effect d. background radiation

I think it is B. Hubble’s law

The correct answer is A. Dark energy.

Explanation:

The dark energy is an invisible form of energy which is said to be the reason for the acceleration in the expansion of the universe. It is measured and experienced by the astronauts that galaxies and stars moving away from the earth that means the universe is expanding.

Since 1998 it is the most accepted hypothesis about the expansion of the universe.

Thus, the correct answer is option A. Dark energy.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.