In the IP addressing scheme that was in use before IPv6 was introduced, what…

Concept. The length of an IP address is not a free choice — it is fixed by the version of the Internet Protocol whose header carries it, because the source and destination address fields in that header have a fixed bit width. Storage is quoted in bytes (octets), and the two units are related by a single conversion: 1 byte = 8 bits, so bytes = bits ÷ 8.

Application. Apply that rule to the scheme named in the question:

1. Identify the scheme. "Before IPv6 was introduced" means the Internet Protocol version that IPv6 succeeded — that is IPv4, standardised in RFC 791.

2. Read off its fixed address width. RFC 791 defines the IPv4 source and destination address fields as 32 bits each.

3. Convert bits to bytes using the conversion above: 32 ÷ 8 = 4.

4. So an address in the pre-IPv6 scheme occupies 4 bytes.

Cross-check. Multiply back: 4 bytes × 8 bits-per-byte = 32 bits, which matches the RFC 791 field width, so the conversion is consistent. A second check comes from dotted-decimal notation: each dotted group holds a value from 0 to 255, i.e. exactly one 8-bit octet, and an IPv4 address is written as four such groups — 4 octets = 4 bytes.

Contrast. The most common slip on this item is answering for IPv6 itself rather than for the scheme that preceded it:

IPv6 addresses are 128 bits, i.e. 16 bytes — a genuinely different value, but it applies only from IPv6 onward. This question asks about the scheme that was in use before IPv6 was introduced, so the 32-bit / 4-byte figure is the one being asked for.