What precautions are necessary when placing a ladder against a building on a sidewalk? select one: a. barricade the area or position a worker in front of the ladder. b. only use scaffolding when working where pedestrians might be walking. c. shut down the sidewalk in front of the building and direct pedestrians to the other side of the street. d. there are no special precautions necessary.

a. Barricade the area or position a worker in front of the ladder.

Explanation:

When one is using a ladder which has to be placed against the building on the sidewalk, the precaution used must be (from the four options) :-

a. Barricade the area or position a worker in front of the ladder.

This is because the area in which the worker is putting the latter is the prone are where the worker or the ladder might hit the pedestrian or any thing which can cause harm to the nature and mankind and that's why, the area must be blocked or defended with an improvised barrier.

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)