The class-C IPv4 address must start with ____.

IPv4 classful addressing (Classes A-E) assigns each class a leading-bit marker of increasing length that together form a prefix-free code — Class A = 0 (1 bit), Class B = 10 (2 bits), Class C = 110 (3 bits), Class D = 1110 (4 bits), Class E = 1111 (4 bits) — so that no class's marker is itself the start of another class's marker. This lets an address be classified by reading its leading bits left to right and stopping as soon as one class's marker is matched, rather than comparing a fixed number of bits for every address.

For Class C specifically, this fixes the address's first three bits at 110: bit 1 = 1 rules out Class A (marker 0), bits 1-2 = 11 rule out Class B (marker 10), and bit 3 = 0 distinguishes it from Class D/E (whose markers continue with a third bit of 1). This restricts the first octet's decimal value to the range 192 to 223 (binary 11000000 to 11011111).

Reading each offered value bit by bit against the markers above, rather than comparing it as a fixed three-character string:

• 10 is itself the complete two-bit marker for Class B — an address beginning this way is already classified Class B before any third bit is considered, so it cannot serve as the (longer) three-bit Class-C marker.

• 101 carries the Class-B marker 10 in its first two bits; under the prefix-free scheme the address is classified Class B at that point regardless of the third bit, so 101 identifies Class B, not Class C.

• 011 opens with the single bit 0, which is the complete Class-A marker on its own — the address is classified Class A immediately, before its remaining bits are even read.

• 110 is the only offered value whose bits, read in order, rule out Class A and Class B and then positively confirm Class C's own three-bit marker.

So, by the classful marker rule, the class-C IPv4 address must start with 110.