Refer to the exhibit. Which subnet mask will place all hosts on Network B in the same subnet with the least amount of wasted addresses?

255.255.255.0 (/24) provides only 254 usable addresses, which is not enough to place all hosts on Network B in a single subnet given the exhibit's host count.

A /23 mask (255.255.254.0) provides 512 total addresses and 510 usable host addresses, which is the smallest power-of-two block that accommodates a host count on Network B greater than 254 but no more than 510. Choosing /22 or larger would waste significantly more addresses, while /24 would be insufficient if the host count exceeds 254.

255.255.252.0 (/22) provides 1022 usable addresses, which is more than twice what Network B needs and wastes a large address block.

255.255.248.0 (/21) provides 2046 usable addresses, an even larger over-allocation that wastes far more addresses than necessary.