Connection of pipes

In the pipe connection shown above, the diameters of pipes $1$ to $7$ are different. Water enters through pipe $1$ and exits through pipe $7$ . If $Q_1$ is the rate of flow of pipe $1$ , $Q_2$ is the rate of flow of pipe $2$ , ... and so on, which of the following is true?

A. $Q_1=Q_2+Q_4+Q_5$

B. $Q_7=Q_2+Q_3+Q_4+Q_5+Q_6$

C. $Q_6=Q_1+Q_5$

D. $Q_7=Q_3+Q_4+Q_6$