Can I suggest reasons for changes shown on graphs or charts?
1. 我可以给出图表中数据变化的原因吗？

No, you shouldn't try to explain reasons for the data in writing task 1. Just describe what you can see.
不可以。在短作文中，你不应该试图解释数据背后的原因。只要描述你看到的即可。

Can we use symbols like $, £ and % in writing task 1?
在短作文中，是否可以使用$、£、%等符号？

Yes, I usually prefer to use these symbols instead of full words like "per cent". For native speakers, it's very normal and natural to do this.
可以。通常来说，我更喜欢使用这些符号，而非类似per cent这样的文字。对于英语为母语的人来说，这种做法非常普遍和自然。

When describing a map (writing task 1), can we use north, south, east, west even if no compass is shown?
短作文中，描述地图时，如果没有出现指南针，是否可以使用东南西北？

Yes, I often do. I think it's fine to assume that the top of a map is north.
可以，我经常这样做。我认为上北下南的假设十分合理。

Do I need to include all of the data in my task 1 essay?
短作文中，我需要把所有数据都写进去吗？

No, the question will always ask you to select key points. There is usually too much data for a 150-word essay. Also, your ability to select key data will impress the examiner.
不需要。作文题目总是要你选择关键点。通常情况下，所有数据对于一篇150字的文章来说显得太多了。此外，你选择关键数据的能力也会给考官留下印象。