In the consumption equation, the slope of the consumption function is represented as:

Option 1: $c$ -> This represents the marginal propensity to consume (MPC), which is the slope of the consumption function.

Option 2: $\bar{C}$ -> This is autonomous consumption, representing the intercept (consumption when income is zero), not the slope.

Option 3: $cY$ -> This represents induced consumption (the income-dependent part of consumption), not the slope.

Option 4: $Y$ -> This is income, the independent variable in the consumption function, not the slope.

Hence, Option 1: $c$ -> In the consumption function C = $\bar{C}$ + cY, the parameter 'c' is the marginal propensity to consume (MPC), which represents the slope. It shows the change in consumption for each unit change in income (ΔC/ΔY). The value of c lies between 0 and 1, indicating that for every additional dollar of income, consumption increases by c dollars. -> correct