Duplicate the circle. Make something like in the picture with the Pen Tool.
Select both with the Selection Tool and click on Divide. Delete the bottom part.
Place it over the original circle. Go to Object > Path >
Offset Path. Use ‘-10 px’. Delete the outside part. Use no stroke and give it a black/white gradient. Set it on Screen.
When you are done, you should have a Help Icon that looks something like this.
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