I'd guess at valve B. more information about the interesting question would help.
Answer:
D. crystalline solid that conducts current under certain conditions
Explanation:
Semiconductors are crystalline solids that has the ability to conduct electrical currents but on certain conditions e.g heat. The conduction of semiconductors is less than that of conductors (metals) but more than insulators (nonmetals), hence, they are said to be intermediates of conductors and insulators in terms of electrical conductivity.
Examples of semiconductors are silicon, boron, carbon, germanium, arsenic etc.
B represents the direction of the magnetic field around the wire
Explanation:
A wire carrying an electric current always produces a magnetic field around itself. The lines of the magnetic field produced by a current-carrying wires are concentric circles around the wire. The magnitude of the field is given by the formula:

where
is the vacuum permeability
I is the current in the wire
r is the distance from the wire
The direction of the field lines is given by the so-called right hand rule, shown in the figure. Basically, the thumb of the right hand is placed in the direction of the electric current, while the other fingers are "wrapped" around the thumb: the direction of the other fingers give the direction of the magnetic field lines.
Learn more about magnetic field:
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Answer:
R = 715.4 N
L = 166.6 N
Explanation:
ASSUME the painter is standing right of center
Let L be the left rope tension
Let R be the right rope tension
Sum moments about the left end to zero. Assume CCW moment is positive
R[5] - 20(9.8)[5/2] - 70(9.8)[5/2 + 2] = 0
R = 715.4 N
Sum moments about the right end to zero
20(9.8)[5/2] + 70(9.8)[5/2 - 2] - L[5] = 0
L = 166.6 N
We can verify by summing vertical forces
116.6 + 715.4 - (70 + 20)(9.8) ?=? 0
0 = 0 checks
If the assumption about which side of center the paint stood is incorrect, the only difference would be the values of L and R would be swapped.