What's the population of Germany?德国的人口有多少？

population 表示“人口”是一集体名词，have population of 表示“有多少人口”。例如：

Our village has population of two hundred of people.

我们村有二百人口。

What's the population of you city?

你们城市有多少人口？

★　What does "standing room only"mean?

What does "standing room only"mean?“只有站的空间”意味着什么？

room 表示“地方”，“空间”，与space 是同义词，后者多指“太空”，room 还表示“房间”。例如：

Is there any room for me to sit?

有我坐的地方吗？

Make room for me,please?

请给我让个地方。

The moon is quite near to us in the space.

太空中，月亮离我们很近。

★　The population problem may be the greatest one of the world today.

The population problem may be the greatest one of the world today.人口问题可能是当今最大的问题。

Problem 表示“问题”，是一种需要解决的问题。Question 也表示“问题”，是一种需要回答的问题。例如：

This problem is too hard,I can't solve（解决）it.

这个问题太难了，我解决不了。

Can you answer my question?

你能问答我的问题吗？

★　A UN report says that the world population will pass six billion by the end of the twentieth century.

A UN report says that the world population will pass six billion by the end of the twentieth century.一份联合国报告说，到二十世纪末，世界人口将达到六十亿。

By the end of…表示“到…底为止”。例如：

We have learned eight hundred English words by the end of last week.

到上一星期为止，我们学了八百个英语单词。

I'll finish my work by the end of this week.

这一周末，我就完成我的工作。