What is the purpose of an isolation coat before varnishing an acrylic painting?

Correct answer: Create a permanent barrier between the painted surface and removable varnish

An isolation coat is a clear, permanent protective layer placed over the finished acrylic surface before a removable varnish. Its governing conservation principle is separation: if the varnish later needs cleaning or removal, the paint film remains protected below the isolation coat. Thus option D is correct. It does not bleach the canvas, instantly dry the picture, or dissolve the colours into one another.