题目内容：
"Even exercise professionals concede halfa point here"(Line 3,Para.2) means "They （ ） ".
A．agree that the calories in a small piece of pastry can be difficult to work off by exercise B．partially believe diet plays a supporting role in weight reduction
C．are not fully convinced that dieting can help maintain one's new weight
D．are not sufficiently informed of the positive role of exercise in losing weight
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