The smallest fraction, which each of 6/7, 5/14, 10/21 will divide exactly is?  Choose the correct choice from the following.
A) 30 / 7	B) 30 / 9	C) 30 / 2	D) 30 / 3	E) 30 / 6

Rationale: "required fraction = l . c . m of 6 / 7 , 5 / 14 , 10 / 21 = ( l . c . m of 6 , 5 , 10 ) / ( h . c . f of 7 , 14 , 21 ) = 30 / 7 answer : a"
Answer: A