Why Chinese is such a difficult/dangerous language

So Mandarin Chinese is a tonal language, meaning not only the pronunciation of a word, but the tone of it, can change the meaning. The most widely used example is the syllable 'ma.'

妈: ma (first/high tone) = mother, mom
麻: ma (second/rising tone) = hemp
马: ma (third/dipping tone) = horse
骂: ma (fourth /falling tone) = to scold, chide

With the characters, of course, it's easy to tell the difference, but without them, you have to rely on the tone of the syllable to know which meaning it is.

So today, at lunch, we saw one of our American classmates at a table in the student center and went to join him. As we sat down, he said, "wo gan mao le." What he meant to say was, 'I have a cold' (我感冒了, wo-dipping, gan-dipping, mao-falling le-neutral tone). However, because he mixed up his tones, he said 我干猫了 (wo-dipping, gan-falling, mao-high le-neutral tone). My German classmate, whose English is pretty good, asked, in English,

"You f*cked a cat?!"