The double-blind laboratory tests means ().
A.nobody taking part in the test knows if the 3G base station is transmitting signals
B.only the subjects in the test know if the 3G base station is transmitting signals
C.no researchers know if the 3G base station is transmitting signals
D.everyone in the test knows if the 3G base station is transmitting signals
A、nobody taking part in the test knows if the 3G base station is transmitting signals