A ladder is resting on a rough ground and leaning against a smooth vertical wall. The force of friction will act

less than

In a screw jack, the effort required to lower the load is less than the effort required to raise the same load.

100 percent

An ideal machine is that in which there is no dissipation of energy in any manner. In an ideal machine, the work output is equal to the work input, i.e., efficiency of an ideal machine is 100%.
In ideal machines mechanical advantage is equal to velocity ratio.

load lifted to the effort applied

the mechanical advantage of a lifting machine is the ratio of load lifted to the effort applied.

all of the above

The efficiency of a lifting machine is the ratio of
output to the input
work done by the machine to the work done on the machine
mechanical advantage to the velocity ratio