The perfect tenses ? bothpresent and past ? areexplained and usedprominently in most of thesereaders. Many introduce thepassive voice, and most featurethe future tense. Nearly all ofthem also include exercises todevelop understanding of thefirst conditional, and someinclude instruction in all threeconditional forms. More modalverbs and more complex verbalconstructions ? using gerundsand infinitives ? are presented.There is a generally higher levelof vocabulary, sometimes quitesophisticated.
