According to the passage, coughing and sneezing ------ .

Ever since Nobel prize-winner Linus Pauling first
advocated vitamin C as a common-cold war weapon
more than 20 years ago, researchers have been busy
trying to verify that claim. But so far, they've found
little evidence that vitamin C prevents colds - in fact,
there are more studies that say it doesn't. But there is
evidence that it can keep coughing and sneezing to a
minimum, and that low levels of vitamin C in the body
may be related to bronchitis.