Which is true about UVA and UVB rays? A. Both rays can be blocked 100% by sunscreen
B. UVA protects the surface, UVB protects beneath the surface
C. UVB rays cause burning, UVA rays cause premature aging
D. UVA rays cause burning, UVB rays cause premature aging

I need help :

I'm pretty sure the answer is c 

Jenny and fred both play a long note on their trombones. a stationary observer hears the sound increasing and decreasing repeatedly in loudness. which of these must be true? the sound waves from the two trombones have slightly different frequencies.the sound waves from the two trombones have the same frequency.the sound waves from the two trombones have slightly different amplitudes.the sound waves from the two trombones have the same wavelength.the sound waves from the two trombones have slightly different velocities.  lolthe answer is          the sound waves from the two trombones have slightly different frequencies.

Answeryellow bile