Question

the inner membrane of which cell organelle is unfolded at several places and why?

Answer 1

HEYA !!

The inner membrane of mitochondria is unfolded to increase the surface area inside the organelle to contain the fluid called matrix.

Answer 2

HEY MATE,
The inner membrane folds over many times and creates layered structures called cristae. The fluid contained in the mitochondria is called the matrix. The folding of the inner membrane increases the surface area inside the organelle.(in your question you said "unfolded" but no organelle is like that)

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