Pick up the correct statement from the following during tunnel excavation,

[A].	Oxygen should not be less than 19.5%
[B].	Carbondioxide should not be more than 0.5%
[C].	Hydrogen sulphide should not be more than 0.001%
[D].	Carbon mono-oxide should not be more than 0.01%
[E].	All of the above.

Answer: Option E

Explanation:

No answer description available for this question. Let us discuss.