Must be true. As shown in the stimulus diagram, if caffeine content is listed, it’s easier to limit intake; if it it’s easier to limit intake, some people would; if people do, their health improves. So “list caffeine content” is a sufficient condition for “improve their health”!

Could be false. Answer choice (B) has a negation issue: it takes a statement from the stimulus (list caffeine content → easier to limit) and negates the sufficient condition. We can’t draw conclusions from negated sufficient conditions—that’s like taking half the contrapositive!

Could be false. The stimulus doesn’t tell us anything about what happens if people have to guess how much caffeine is in their soft drinks; we only have information about what happens if the caffeine content is listed.

Could be false. The stimulus doesn’t tell us anything about people who wish to eliminate their caffeine intake; we only have information about some people who would limit their intake if soft drink labels listed exact content.

Could be false. While we know that some people’s health would improve if they could see soft drinks’ caffeine content on the label, we know nothing about people outside that group—maybe some people’s health would worsen, or maybe everyone else’ health would stay the same.