So, the comparison is really between 2c and c.

Why not we cancel both C from both side and rest we get 2 and 1. So A is greater !!!!!!!!!!!!!!!!

Sometimes a quick approach is looking for values that make the two quantities equal (see video below).

So, for example, it could be the case that a = b = c = 0, In which case the two quantities are equal.
It could be the case that a = 4, b = 2 and c = 1, In which case the two quantities are NOT equal.

Answer: D

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Because $c$ can be negative or positive. You can cancel $c$ from both sides only when you are hundred percent sure the value of $c$ is positive.

If $a,b \text{ and } c \text{ are positive }$, then

$a=2b$

$b = \frac{a}{2}$

$a = 4c$

$c = \frac{a}{4}$

$Quantity A = a + \frac{a}{2}$

$Quantity B = a + \frac{a}{4}$

Clearly $Quantity A > Quantity B$

But if $a,b \text{ and } c \text{ are negative }$, we are going to get the opposite

$Quantity A = -a -\frac{a}{2}$

$Quantity B = -a -\frac{a}{4}$

Clearly $Quantity B > Quantity A$

The answer is D. There exists no relationship between the two quantities.