Which first-line of defense uses acids to kill pathogens?

Stomach Acid

Explanation:

Stomach acid destroys bacteria that have been eaten and parasites. From the bladder region, the urine flow flushes out contaminants. In combating bacteria, skin, tears and mucus are part of the first line of defense. They continue to shield us from diseases attacking us.

organisms are more likely to be more preserved in mud than sand because mud is moist and wet, while sand is very dry.