27) E

Time taken for three complete oscillations = 0.6
Time taken for one complete oscillation = 0.6 ÷ 3 = 0.2
Time taken for two complete oscillations = 0.2 x 2 = 0.4

Distance covered by two complete oscillations = 60m

Speed = Distance ÷ Time
Speed = 60 ÷ 0.4 = 150 m/s