The given quadrilateral is a rhombus because all the sides are equal.

Therefore,

Area of rhombus = \(\frac{1}{2}\) × d₁ × d₂

(Here, d₁ = diagonal 1, and d₂ = diagonal 2)

According to question

d₁ = 2.5 and d₂ = 3 cm

Hence,

Area of quadrilateral = \(\frac{1}{2}\) × 2.5 × 3

                              = \(\frac{1}{2}\) × 7.5 = 3.75 cm²

Hence, option a is correct.