The statement that is true about Planck's Law is that the frequency of the emitted light is directly proportional to the energy given off by the electrons. The correct answer is B.
When vapor pressure equals atmospheric pressure, it's called boiling point of that liquid.
Volcanic activity is likely to happen when two plates pull apart form one another. When the surface of the Earth is separated, the magma within will pour out.
Answer: B. Volcanic Activity