一头牛的基本组成单位是（  ）

$\frac{3}{1.5}$ ＝ $\frac{x}{4}$

x＝____

    It is interesting to visit another country, but there are some problems when we don't know the 1very well.It may be 2 to talk with the people there. We may not know how to use the telephone in the country that we are visiting. We may not know how to buy 3 we need. In a4country we might not know where to eat or what to order in a 5 It is not easy to decide how6to tip (给……小费) waiters or taxi drivers. When we need help, we might not know how to ask for help.It is not pleasant to have an experience7that. 8a short time, however, we learn what to do and what to 9We learn to enjoy life in another country and then we may feel 10 because we have to leave.