The answer is c. 16x2 + 24xy + 9y2.
Since we need trinomial (three term expression) choices a and b are incorrect because they have only two terms.
So, our square trinomial is a² + 2ab + b² or a² - 2ab + b²
a² + 2ab + b² = (a + b)²
a² - 2ab + b² = (a - b)²
Let's check choices c and d:
c) 16x² + 24xy + 9y²
a² = 16x²
a² = (4x)²
a = 4x
b² = 9y²
b² = (3y)²
b = 3y
a² + 2ab + b² = (4x)² + 2 * 4x * 3y + (3y)² = 16x² + 24xy + 9y²
CORRECT
d) 49x² - 70xy + 10y²
a² = 49x²
a² = (7x)²
a = 7x
b² = 10y²
b² = (y√10)²
b = y√10
a² + 2ab + b² = (7x)² + 2 * 7x * y√10 + (y√10)² = 49x² + 14xy√10 + 10y²
INCORRECT
So, c) is correct answer