B. He and I made a delicious dinner for our parents.
Hey there!
<em>Many</em> can be used as a pronoun or adjective. It describes only <em>countable</em> nouns.
In this case, <em>many</em> is an adjective to<em> items, </em>because it is <em>describing it</em>.
<em>Hope this helps!</em>
~Fluerie