Which of the following sets in $\mathbb{R^2}$ have positive Lebesgue measure?

Question

For two sets $A, B \subseteq \mathbb{R^2}$ we define $A+B = \{a+b \mid a \in A, b \in B \}$. Which of the following sets in $\mathbb{R^2}$ have positive Lebesgue measure?

A. $S=\{(x,y)|x^2+y^2=1\}$

B. $S=\{(x,y)|x^2+y^2<1\}$

C. $S=\{(x,y)|x=y\}+\{(x,y)|x=-y\}$

D. $S=\{(x,y)|x=y\}+\{(x,y)|x=y\}$