In my opinion, there are so many advertisements everywhere we go, but many/much of them are ineffective.
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Which one do we have to use, many or much?
Many. Much suggests quantity, like, "How much milk is left in the bottle?" "Many" also may mean quantity, or numbers, but implies a large or a specific amount, as in, "How many crayons are in that box."
http://www.merriam-webster.com/dictionary/many
http://www.merriam-webster.com/dictionary/much