Installing the rain gauge

Source A: an original contemporary non-fiction-style account.

Our school weather club fixed a rain gauge in the courtyard in October. We chose an open patch away from the drainpipe, then used a spirit level to check that the base was flat. The caretaker supplied a short wooden post, but the science teacher brought the gauge itself. My job was to read it at nine each morning and enter the amount on a chart beside the classroom door.

On the first Friday, fallen leaves blocked the opening. I removed them before taking a reading, and the teacher marked that day's result as unreliable because some rain might not have entered. We emptied the gauge after every reading. At the end of the month, the class compared our chart with figures from the nearest weather station. They were not identical, which disappointed me until we discussed how location and small measurement errors could affect the result. Keeping a record had proved more interesting than simply deciding whether a day was wet.

Refer to the whole of Source A. Choose the four true statements below. Write their four letters in the answer box. Choose no more than four; if more are given, only the first four distinct letters will be marked.