Explanation:

- The first thousand days can determine the trajectory (1)______ a child’s life.

The words that can fill this blank effectively include prepositions such as "of," suggesting a path or direction for a child's life.

- After food for the body (2)______ taken care of, we should provide food for (3)______ mind.

This sentence points to ensuring mental nourishment after physical needs are met.

- Select the most appropriate option to fill in blank no. 3.

- Option 1: a - implies "a" general type of mind, which doesn't fit.

- Option 2: the - specifies "the" mind being talked about, i.e., the child's mind.

- Option 3: some - suggests "some" mind, which is vague and incorrect.

- Option 4: that - typically used for specifying or connecting topics, unsuitable here.

- Correct Option: Option 2: the

Using "the" specifies that "the mind" refers to the same child's mind already being discussed.