What should be the size of the internal door of a residential building?

• A. (0.9 m x 2 m) to (1 m x 2 m)
• B. (1.0 m x 2.9 m) to (2.1 m x 3 m)
• C. (1.0 m x 3 m) to (2.1 m x 3 m)
• D. (0.9 m x 1 m) to (1 m x 3 m)