The history club surveyed 75 students about the number of history courses in which they were enrolled and the length of time it took them to complete an exam. Classify the random variables from the survey.

Number of history courses, continuous; length of time to complete exam, continuous
Number of history courses, continuous; length of time to complete exam, discrete
Number of history courses, discrete; length of time to complete exam, continuous
Number of history courses, discrete; length of time to complete exam, discrete
Unable to determine from information given