Self-study
Each of the many people who participated in the town's annual spring cleanup received a community recognition certificate. ███████ ███ ██████ ███████ ████ █████ ██ ███ ████ ████ ██ ███ ████████ ████ █████ ██ ████ ████ █████ ███ ██ █████ ████ ██████ ███████ ████████████ ███ ███ ███ ██████ ██ ███ ██████ ████████ ████████
Summary
Every person who participated in the town’s annual spring cleanup received a community recognition certificate. However, there are some spring cleanup participants who are not active in the town’s artistic circles because the spring cleanup took place at the same time as the downtown arts fair. 
Notable Valid Inferences
Some people who received community recognition certificates are not active in the town’s artistic circles.
21.
If the statements above are █████ █████ ███ ██ ███ █████████ ████ ██ █████
a
Some of the ███████ ███ ███ ██████ ██ ███ ██████ ████████ ███████ ████████ █████████ ███████████ █████████████
Could be false. We know that some people who are not active in the town's artistic circles participated in the cleanup. But this doesn't tell us anything about people who are active in the town's artistic circles. We don't know anything about these people.
b
Not all of █████ ███ ████████ █████████ ███████████ ████████████ ███ ██████ ██ ███ ██████ ████████ ████████
Must be true. We know everyone who participated in the cleanup got a certificate. And some of the people who participated in the cleanup aren't active. That proves some people who got the certificate aren't active. 
c
No participants in ███ ████████ ████ ████ ████████ █████████ ███████████ █████████████
Could be false. We know that the arts fair and the spring cleanup took place at the same time, but we cannot assume that it is impossible for a person to participate in both events.
d
No person who ████████ █ █████████ ███████████ ███████████ ███ ███ ████████████ ██ ███ ██████ ████████
Could be false. This answer choice confuses sufficiency for necessity. Although we know that everyone who participated in the cleanup got a certificate, this doesn't imply that everyone who got a certificate must have participated in the cleanup.
e
Persons who are ██████ ██ ███ ██████ ████████ ███████ ███ ███ █████████ ████ ███ ██████ ████████████
Could be false. We don't know anything about a person’s concern with the environment. Moreover, we cannot assume that people who didn’t participate in the cleanup are not concerned with the environment.