The centre of gravity of a trapezium with parallel sides a and b lies at a distance of y from the base b, as shown in the below figure. The value of y is

A. h [(2a + b)/(a + b)]

B. (h/2) [(2a + b)/(a + b)]

C. (h/3) [(2a + b)/(a + b)]

D. (h/3) [(a + b)/(2a + b)]

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