To get the total resistance in a parallel circuit, you need to remember that unlike in a series, you do not just merely add the resistances. You need to get the reciprocal first of each resistance and add them together.

After adding them, you will get the reciprocal again and then compute for the value. The problem says that there are 4 resistors in the circuit that have a resistance of 75.

Add up the numerator and copy the denominator:

Then get the reciprocal to get the total resistance:

The answer to your question then is A. 18.8.
D. March because it is just below the 1 million marker on the graph and it is the only one that low.
It shortens so that the tips reach faster
You've got some UHF radio waves at the long end of that range. But most of the range consists of <em>microwaves</em>.
For example: In the US, the "microwave oven" kitchen appliance cooks with radiation at a wavelength of about 12.2 cm .