Reason: This question is a brain teaser, and the answer to the question comes from a two-part allegorical saying, "Burning incense behind your wife's back-thankless", which was originally a two-part allegorical saying of logical reasoning;

Because it takes a lot of effort to burn incense in the temple behind my daughter-in-law's back, and it is not recognized. It is also in line with this meaning to be thankless, and the topic is a brain teaser. If the word "hard" is used as a name, it will become a daughter-in-law to burn incense. This "person" is thankless.

Extended data:

Common brain teasers are:

1, there is a word that everyone will mispronounce when they see it. What's this word? A: This is the word "wrong". This question doesn't mean spelling pinyin wrong, but which word is pronounced "wrong".

2. What must everyone do seriously every day? Answer: Sleep, because you can't sleep without serious sleep, and once you fall asleep, you sleep seriously.

3. Who is always afraid of taking a bath? Answer: Clay figurines, because clay figurines are made of clay, will melt when they touch water.