Answer:
C
Step-by-step explanation:
49x² + 28xy + 4y² ← is a perfect square of the form
(ax + by)² = a²x² + 2abxy + b²y²
49 = 7² ⇒ a = 7 and 4 = 2² ⇒ b = 2
2ab = 2 × 7 × 2 = 28
Hence
49x² + 28xy + 4y² = (7x + 2y)²
with factor 7x + 2y ⇒ C
