#### Answer

a. No. Yes. No. Yes.
b. $R=\{(2,6), (2,8), (2,10), (3,6), (4,8)\}$
c. The domain is $A=\{2, 3, 4\}$. The range is $B=\{6, 8, 10\}$.
d.

#### Work Step by Step

$(x,y)$ is an element of $R$, or $x\ \ R\ \ y$, whenever $y$ is divisible by $x$. Note that a relation $R : X\ \ to\ \ Y$ has domain $X$ and codomain $Y$, even if not every element of $X$ and/or $Y$ is in $R$.