When the Moon is on an observer's meridian at 9 A.M., the Moon is in the ______________ phase.
a. waning crescent
b. waning gibbous
c. waxing crescent
d. waxing gibbous
Question 2
Complete destructive interference occurs for two waves of the same amplitude and frequency when the waves are ______________ degrees out of phase.
Fill in the blank(s) with correct word