【单选题】

Losing weight can seem like an unwinnable war. You know you need to eat less and exercise more, but that’s (1) impossible when everything in your life—from job stress to the temptation of fast and (2) foods—encourages you to do the (3) .A、healthy diet and regular exercise are certainly the best weapons against weight gain, (4) the fact is that sometimes they aren’t enough.And that’s (5) science may someday be able to help.

In various research labs, researchers are closely looking (6) the biological mechanisms of obesity, (7) why some bodies store fat so (8) , and why others are better at burning the calories they (9) . They are discovering a surprising (10) of metabolic and physiologic factors that contribute to weight: did you know, for instance, that your intestines are full of bacteria that can (11) or restrain weight gain to some extent Or that the brown fat—which is (12) in newborns—actually burns a lot of calories, (13) the traditional white fat commonly stored in bellies
These and other findings about the biology of weight gain could be the (14) to slimming our collective waistline, if scientists can someday use them to (15) better treatments for obesity. (16) we could use the help: in the decade between the year of 1991 and that of 2000, the (17) of overweight adults in the U.S. increased by 61%. Last year, 30% of children in 30 states (18) the scales as either overweight or obese. "We just don’t have enough physicians to treat all the obese people," saysDr. Michael Jensen, professor of medicine.
If the latest findings from obesity labs prove as (19) as they are promising, they could in the future make the job of fighting obesity easier for (20) and patients, and help all of us get an extra boost from our diet and exercise programs.
A．so
B．but
C．while
D．because