1. Why don't you start first?
2. Why not start first?
3. How about starting first?
4. What do you think about/of starting first?
5. How do you feel about starting first?
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Are they all grammatical?
2. Why not start first?
3. How about starting first?
4. What do you think about/of starting first?
5. How do you feel about starting first?
---------------
Are they all grammatical?