831. What is the common name for the drug acetyl salicylic acid?
832. The sounds of which frequency are human beings most sensitive?
A. 400 hertz
B. 20 hertz
C. 20000 hertz
D. 5000 hertz
833. On which disease did Robert Koch work?
834. Which of the following gases do plants and trees give out during photosynthesis?
D. Carbon dioxide
835. Which of the following is not a waterborne disease?
836. Name the branch of science which deals with the study of sound and sound waves?
837. Which metal is added to steel to make it stainless steel?
838. What is the range, in hertz, of the normal human hearing?
A. 10 Hz to 10 kHz
B. 20 Hz to 20 kHz
D. 40 Hz to 40 kHz
839. Who invented Logarithm Tables?
A. John Napier
B. John Doe
C. John Harrison
D. John Douglas
840. How many pairs of walking legs does a cockroach have?