Which one of the following statements is not correct with regard to heading and hench-ing method of tunnelling.

[A].	Driving of tunnel is done in two portions of its section
[B].	Driving the top portion is done in advance of the bottom portion.
[C].	After driving the top portion 3 m to 3.5 m holes are drilled into the head and bench.
[D].	The holes in head and bench are loaded together with explosive for blasting.
[E].	Firing of head holes is done just before the bench holes are fired.

Answer: Option E

Explanation:

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