When the nuclear reactions begin making too little energy in a star, by virtue of the natural thermostat, the star:
A) would expand slightly.
B) would reduce its central temperature.
C) would increase its density.
D) would increase the mass by a factor of 2.
Question 2
Only photons with wavelengths _____ can ionize hydrogen.
A) shorter than 91.2 nm
B) longer than 104.3 nm
C) shorter than 40 nm
D) longer than 80 nm