To solve the problem, let's carefully compare the slopes of the given lines:
1. We have two lines:
- The first line is [tex]\( y = mx - 4 \)[/tex].
- The second line is [tex]\( y = x - 4 \)[/tex].
2. The general form of a linear equation is [tex]\( y = mx + b \)[/tex], where [tex]\( m \)[/tex] is the slope and [tex]\( b \)[/tex] is the y-intercept.
3. For the first line [tex]\( y = mx - 4 \)[/tex]:
- The slope is [tex]\( m \)[/tex].
4. For the second line [tex]\( y = x - 4 \)[/tex]:
- The slope is [tex]\( 1 \)[/tex] because [tex]\( y = x - 4 \)[/tex] can be rewritten as [tex]\( y = 1x - 4 \)[/tex].
5. According to the problem, the slope of the line [tex]\( y = mx - 4 \)[/tex] is less than the slope of the line [tex]\( y = x - 4 \)[/tex].
- This means [tex]\( m \)[/tex] is less than [tex]\( 1 \)[/tex].
6. Therefore, the condition that must be true is:
[tex]\[ m < 1 \][/tex]
So out of the given options, [tex]\( m < 1 \)[/tex] is the correct answer.