Question

He sat under the boughs of a spreading tamarind tree (use modal auxiliary showing habitual action in the past)

Answer 1

Answer:

He would sit under the boughs of a spreading tamarind tree.

or

He used to sit under the boughs of a spreading tamarind tree.

Explanation:

Modal 'would' is used to talk about things or actions that often happened in the past.  

'Used to' is a modal verb that is used to say that an action happened continuously or frequently during a time in the past.  

Example:

I used to do lots of exercise when I was young.