public int getTense ( String posTaggedSentence ) {
        int count = 0;
        String[] wordsAndTags = posTaggedSentence.split(" ");
        int size = wordsAndTags.length;
        for ( int i = 0 ; i < size ; i++ ) {
            String temp = wordsAndTags[i].substring(wordsAndTags[i].indexOf('/')+1);
            if ( temp.length() == 3 && temp.equals("VBD") ) {
                count++;
            }
        }
        return count;
    }