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:

"social stratification refers to the way people are ranked and ordered in society. in western societies, stratification is primarily seen and understood as a result of socioeconomic status, which produces a hierarchy in which access to resources, and possession of them, increases from the lower to the upper strata"

the earth’s crust is broken into separate pieces called tectonic plates (fig. 7.14). recall that the crust is the solid, rocky, outer shell of the planet. it is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. both types of crust rest atop solid, upper mantle material. the upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.

each tectonic plate is free-floating and can move independently. earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. the term fault is used to describe the boundary between tectonic plates. most of the earthquakes and volcanoes around the pacific ocean basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. other observable results of short-term plate movement include the gradual widening of the great rift lakes in eastern africa and the rising of the himalayan mountain range. the motion of plates can be described in four general patterns:

collision: when two continental plates are shoved together

subduction: when one plate plunges beneath another (fig. 7.15)

spreading: when two plates are pushed apart (fig. 7.15)

transform faulting: when two plates slide past each other (fig. 7.15)