C
Step-by-step explanation:
The equation of a line in slope- intercept form is
y = mx + c ( m is the slope and c the y- intercept )
Rearrange 6x + 10y = 8 into this form by subtracting 6x from both sides
10y = - 6x + 8 ( divide all terms by 10 )
y = - x + ← in slope- intercept form
with slope m = - → C