Which matrix is commonly used in gel electrophoresis?

The correct answer is Option (1) → Agarose

Gel electrophoresis separates DNA fragments. The fragments are negatively charged, so in an electric field they move towards the anode through a matrix. The most commonly used matrix is agarose, a natural polymer extracted from sea weeds. The agarose gel acts like a sieve, so smaller fragments move farther.

NCERT Extract:
Separation and Isolation of DNA Fragments – “… Since DNA fragments are negatively charged molecules they can be separated by forcing them to move towards the anode under an electric field through a medium/matrix. Nowadays the most commonly used matrix is agarose which is a natural polymer extracted from sea weeds. The DNA fragments separate (resolve) according to their size through sieving effect provided by the agarose gel.”