Question

When electric field lines enter the closed surface, electric flux will be
a)positive
b)negative
Explain...otherwise I'll report

Answer 1

The negative flux just equals in magnitude the positive flux, so that the net, or total, electric flux is zero. If a net charge is contained inside a closed surface, the total flux through the surface is proportional to the enclosed charge, positive if it is positive, negative if it is negative.

Answer 2

Since the surface is closed therefore the area vector will be outwards.

Since area vector is outwards and electric field in inwards

Therefore

Φ=E.dA

=-E.dA

therefore it will be negative