Which modification of root does not store food?

Choose the correct sentence.

The cells of this region of the root are the smallest.

In $Ipomoea\, batatas$ (Sweet potato),the food is stored in:

In dicotyledonous plants and monocotyledonous plants, the root systems are of the ...... and ...... types, respectively.

What is meant by modification of root? What type of modification of root is found in the:
$(a)$ Banyan tree
$(b)$ Turnip
$(c)$ Mangrove trees