题目内容：

阅读下面材料，在空白处填入1个适当的单词或括号内单词的正确形式。

In 1969, Armstrong 1.(successful) set foot on the Moon. This was 2. first time anyone had walked on the surface of another world. More astronauts（宇航员）reached the Moon later, but nobody 3.(visit) it since 1972. Do you think it’s time we went back?

4.(explore) of the Moon did continue after the astronauts left, but by robots instead 5. people. Satellites have helped us learn more about our neighbour and shown that there 6.(be) even more exploring to do, but astronauts would be needed!

The problem is that sending humans to the Moon is very expensive. Even with all the new technology since Armstrong’s time, it would cost so much for people 7.(return) to the Moon.

ESA (European Space Agency) wants to change that. ESA’s idea isn’t just to make the spaceships 8.(they), but also to work with businesses here on Earth. ESA also wants to help businesses on Earth develop tools and technology 9. will allow people to live on the Moon. If we can use resources（资源）on the Moon, then journeys there will be much 10.(cheap). For example, what if we could get to water hidden deep within Moon rocks?