B
the equation of a line in slope-intercept form is
y = mx + c ( m is the slope and c the y-intercept )
y = 5x + 3 is in this form with slope m = 5
To decrease the slope we require a smaller, positive value for m
y = x + 3 has m = 1 which is less than 5 and positive
y = x + 3 is less steep than y = 5x + 3