Beets do have starch.
Beetroot contain many compounds; it is not a single substance. For details (for red beetroot) see this link.
No, fish does not contain starch. Only plants contain starch.
No, it does not contain starch.
Yes it does contain starch.
no. It depends on the type of chocolate, but it many cases, yes it does contain starch.
It does contain starch
No. Water contains nothing but water. It can contain starch if starch is added to it.
No, onions do not contain starch. They primarily consist of water, fiber, and various vitamins and minerals.
Yes it contains starch
Peas contain starch as it is used is used for the storage of carbohydrates.
No, mushrooms do not contain starch. They primarily consist of water, fiber, and protein.
Yes, it contains starch and starch is a polysaccharide.