1.Which of the following experimental techniques reduces the systematic error of the quantity being investigated? A.timing a large number of oscillations to find a period B.measuring the diameter of a wire repeatedly and calculating the average C.adjusting an ammeter to remove its zero error before measuring a current D.using a metre rule graduated in 0.5 mm rather than 1 mm to measure diameter 2.In an experiment to determine the period of oscillation,T, of an oscillation, the time ,t ,taken. It is found that the time for 20 complete oscillations is 36.5 +/- 0.2 s.Which of the following sattements is/are correct? A.The reading error in t can be reduced by counting 100 oscillations. B.The percent error in T is the same as that in t. C.The period T determined should be quoted as 1.83 +/- 0.01 s.