Which of the following describes a nose down angle of 45 degrees with a heading of 45 degrees?

The correct answer describes a steep descent. In aviation terms, a nose-down angle of 45 degrees indicates that the aircraft is oriented downward significantly, which reflects a steep descent path. The heading of 45 degrees refers to the direction the aircraft is facing, but the critical aspect here is the nose-down attitude. Such an angle typically suggests that the aircraft is in a rapid descent, which is consistent with the characteristics of a steep dive or descent.

In contrast, other options represent different flight configurations. A standard climbing position would involve an upward pitch rather than a nose-down angle. Balanced horizontal flight requires a level attitude, where the aircraft maintains altitude without climbing or descending. An approach to landing could involve a descent, but usually at a more controlled and gradual angle rather than a steep descent of 45 degrees. Thus, the description of a nose-down angle of 45 degrees aligns most accurately with a steep descent.