Which of these happens to the wave when it travels from medium 1 to medium 2?

its energy increases
its amplitude increases
its frequency decreases
its wavelength decreases

its wavelength decreases

Explanation:  A wave is an oscillating disturbance of some physical magnitude in space and periodic in time. The spatial oscillation is characterized by its wavelength, while the time elapsed in a complete oscillation is called the wave period, and is the inverse of its frequency. Wavelength and frequency are related to the speed with which the wave propagates.

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."

answer; strength of association;