When Using the Venn Diagram for Determining Length Seven Binary

Multiple Choice

When using the Venn diagram for determining length seven binary code words for length four messages, which of the following are true statements?
I: Every code word has an even number of 1s.
II: Every possible string of seven binary digits is a code word.
III: Every possible string of seven binary digits can be read as a code word or a code word with a single-digit error.

A) I only
B) I and III only
C) II only
D) III only