Step 1: Understanding the Concept:
Two arbitrary constants mean the differential equation is of order 2. Degree is the power of the highest order derivative after clearing radicals and fractions.
Step 2: Differentiate twice:
\[ 2(y-a)y' = 4 \Rightarrow (y - a)y' = 2 \]
\[ y'^2 + (y-a)y'' = 0 \]
Step 3: Eliminate a:
From the first, \(y - a = \dfrac{2}{y'}\). Substitute:
\[ y'^2 + \frac{2y''}{y'} = 0 \Rightarrow y'^3 + 2y'' = 0 \]
Step 4: Read order and degree:
The highest derivative is \(y''\) (order 2), and it appears to the first power. So the degree is 1. Options (B) and (C) use the power 3 of \(y'\), which is a lower-order derivative.
Final Answer:
The equation y'^3 + 2y'' = 0 has degree 1.
\[ \boxed{\text{(A) }1} \]