Which production tree valve should not be operated in normal operations?

Which production tree valve should not be operated in normal operations? Correct Answer Lower master valve

There are two types of master valves present in the Christmas tree. The lower master valve is generally used as a backup at the time when the upper master valve stopped working when there exists any type of leakage.
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Related Questions

A tree is cut partially and made to fall on ground. The tree however does not fall completely and is still attached to its cut part. The tree top touches the ground at a point 10m from foot of the tree making an angle of 30°. What is the length of the tree?