The signal man assisting the crane operator has his forearm vertical, forefinger pointing up, and moves his hand in a small horizontal circle. this is the signal to

a. extend
b. lower
c. hoist
d. swing

During crane operation, the the operator uses the assistance of the signal man in other to carry out a successful operation, oral communication isn't effect due to noise and thus non-verbal signs are employed. The information passed with forearm vertical, forefinger pointing up, and moves his hand in a small horizontal circle

tells the operator to hoist.

Therefore, the signal mde by the signal man tells the operator to hoist.

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The signal being given by the signalman with his forearm vertical, forefinger pointing up and moving the hand in horizontal circles is the signal to hoist.

Explanation:

answer; /// all of the above;