How to use multiple search terms in TweetSharp

Question

I have just started playing with TweetSharp. This is a piece of the code I am using (with A, B, and C representing my actual search terms):

SearchOptions searchOptions = new SearchOptions { 
    Q = HttpUtility.HtmlEncode("A or B or C"),
    //Q = HttpUtility.HtmlEncode("A"),
    Count = 100,
    Resulttype = TwitterSearchResultType.Recent
};

With this version, I do not see any results. However, if I comment the top Q line and uncomment the second Q line, I do get results. Why would TweetSharp (or Twitter) not like my less restrictive search parameters?