Please help fast *15 pts* What does "stimulated emission of radiation" mean?

A. Radioactive particles in a laser emit gamma rays of the same wavelength.

B. Gas particles in a laser emit coherent light when bombarded with X-rays.

C. Elctromagnetic currents are produced by neon particles when they bump into helium particles.

D. Gas particles in a laser emit photons of light when exposed to an electric current.

The particle p starts from rest at point a at time t = 0 and changes its speed thereafter at a constant rate of 2.8g as it follows the horizontal path shown. determine the magnitude and direction of its total acceleration (a) just before point b, (b) just after point b, and (c) as it passes point c. state your directions relative to the x-axis shown (ccw positive) and choose the angle with the smallest magnitude.