Help me on this writing question please :)

Test Preparation SAT Preparation
1

<p>(Today) a medial doctor must often (make a choice) between (engaging in) private practice (or) engaging in research. (No Error)</p>

<p>I know the answer is d, but for what reason? and what would the correction be?</p>

2

<p>It should be "and".</p>

3

<p>Like "between A OR B" and "between A AND B". The latter is the correct usage. "Or" is incorrect.</p>

4

<p>oh i see now, thank you!</p>