UPSC Civil Services 2017 Prelims General Studies Paper I

Nature is governed by four fundamental forces electromagnetic, strong, weak and gravitational. Standard Model explains the first three forces. (TheHindu, 2017, April)
● Event horizon is the imaginary boundary surrounding the black hole from beyond which light cannot escape and The singularity constitutes the centre of a black hole and is hidden by the object's "surface".
● All these point to answer "A".