单项选择题

Passage 1
Questions 6 and 7 are based on the passage you have just heard.
[听力原文]6-7
Finding enough meat was a problem for primitive man Keeping it when it was scarce was just as hard, Three ways were found to keep meat from spoiling: salting, drying, and freezing.
People near salty waters salted their meat. At first, they probably rubbed dry salt on it. but this preserved only the outside. Later they may have pickled their meat by soaking it in salt water.
In hot, dry lands, men found that they could eat meat that had dried while it was still on the bones. They later learned to cat meat into thin stops and hang it up to dry in the hot air
Men in cold climates found that frozen meat did not spoil. They could leave their meat outside and eat it when they pleased.

How many methods are mere mentioned in the article to preserve the meat（）

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