The correct answer is B. 1,000 Hz.
The frequency of a wave is the number of cycles it completes per unit of time. It is measured in hertz (Hz), which is defined as one cycle per second. The period of a wave is the amount of time it takes for one cycle to complete. It is measured in seconds.
The frequency and period of a wave are inversely proportional. This means that if the frequency increases, the period decreases, and vice versa.
In this case, the period is given as 0.001 second. This means that the wave completes one cycle every 0.001 second. The frequency is therefore 1,000 Hz, which is equal to 1/0.001.
The other options are incorrect because they do not correspond to the given period. Option A is the period itself, not the frequency. Option C is 10 times the frequency, which is not possible because the frequency is already an integer. Option D is 10 times the period, which is also not possible because the period is already a very small number. Option E is simply incorrect.