The answer to this is C. 5 division of EEG paper is equal to one second in time. In the given, it says that instead of 15mm/second, it will be 30mm/second. In 15mm/second, the 5 division of EEG paper is equal to 200 milliseconds. Since we are doubling the numbers from 15 to 30, we would also double the milliseconds which will amount to 400 milliseconds. The numbers will increase or decrease depending on the numbers that will be used.
For example, it will be higher than the previously mentioned numbers. Hopefully, the explanation of the answer to this question will be clear enough. The numbers may also change if 1/2 second would be measured.