Multi-select problem: How does the next paragraph end?

How to improve your intelligence
Try new things.
Novelty stimulates the brain, so being open to new experiences is important to boosting your intelligence. New experiences tend to increase neural activity in the brain, which can help improve intelligence over time.

Choices:
[a]. Be open in your day-to-day life. If a coworker invites you to see a band you've never heard, go..
[b]. Research shows that outgoing people feel more talkative and more engaged. The brain is stimulated by new things and new situations, so engaged with exciting new concepts is important for a positive mind..
[c]. Try trying new physical activities that you're not used to. Try a new sport or a hobby you've never tried before..
[d]. Explore new things that you have not thought of before to increase your optimism. Search online to find something that interests you..
[a].