Q38

Consider a Boolean function $f(w,x,y,z)$. Suppose that exactly one of its inputs is allowed to change at a time. If the function happens to be true for two input vectors $i_{1}=\left \langle w_{1}, x_{1}, y_{1},z_{1}\right \rangle$ and $i_{2}=\left \langle w_{2}, x_{2}, y_{2},z_{2}\right \rangle$ , we would like the function to remain true as the input changes from $i_{1}$ to $i_{2}$ ($i_{1}$ and $i_{2}$ differ in exactly one bit position) without becoming false momentarily. Let $f(w,x,y,z)=\sum (5,7,11,12,13,15)$ . Which of the following cube covers of $f$ will ensure that the required property is satisfied?