Assertion: There is concentration of industries in Mumbai, Chennai, Delhi and in and around Kolkata.
Reasoning: It was due to the fact that they initially became the nodal point having transport links.

Both Assertion (A) and reasoning (R) are correct and R is the correct explanation of A.

There is concentration of industries in Mumbai, Chennai, Delhi and in and around Kolkata. It was due to the fact that they initially became the nodal point having transport links. The industries shifted to interior locations, only when railway lines were laid. All major industrial plants are located on the trunk rail routes.