Sentence:  It must be remembered , however , that there are <WSD>many</WSD> agents for which there is no solid immunity and a partial or low-grade immunity may be broken by an appropriate dose of agent . 
Meaning of the word marked with <WSD> tags:  a quantifier that can be used with count nouns and is often preceded by `as' or `too' or `so' or `that'; amounting to a large but indefinite number