Yes, type "U" refers to Unknown for the Nominal Annual Rate.

是的，“U”型指的是未知的名义增长率。

youdao

U - number of unknown answers in the first pass of the repetition, i.e. the number of questions that have one or more dots in their first column of the repetition scores field.

U -没答对问题的个数，也就是在重复学习评分栏里有一个或多个点的问题个数。

youdao

And last year they saw how the rare hantavirus, once unknown in the U. s., emerged from mice to kill 30 people in as many as 20 states.

而去年，他们见识到罕见的病毒性流感，美国人过去完全陌生的病毒，如何从老鼠身上传出，在广达20个州境内夺走了30条人命。

youdao

First of all, that bearded man who hosts the spots to his French soccer legend, Eric Cantona, who is totally unknown to U.S. viewers.

NPR: Slate's Ad Report Card: Soccer Stars in the Spotlight

The concept of the Protector was largely unknown in the U.S. and nearly always confined to offshore trusts thought the 1990s.

FORBES: Trust Protectors -- What They Are And Why Probably Every Trust Should Have One

At the time, Asus was a relative unknown in the U.S. cellphone market though its PCs, particularly its Eee PC netbooks, were popular among Americans, explains Lin.

FORBES: Asus Tried Windows Phone 7 Two Years Ago, Assessing Whether To Try Again