Please expand on your question...
Running for the bus, the rain began to pour.
If you really think about, it's saying that the rain is running for the bus, which makes NO sense. Here, read it again...
<em>Running for the bus, the rain </em>began to pour.
The author wasn't specific about <em>who </em>exactly was running for the bus.
Not sure if it asks you to do this, but if you were to change it and make it agree, it would be "<u><em>As I was running for the bus</em></u><u>,</u> the rain began to pour." There're other ways to write it of course, but the point is that now you know who actually ran for the bus, and it makes sense.
My question was deleted because it was "incomplete", but I'll answer again.
Simple
This sentence is simple because it contains one singular idea. It may be incorrectly identified as compound because the subject is compound (Forest rangers and volunteers). This is an easy mistake.
Hope this helps!! Good luck, mate. :)
