Übung D: For a blind date, you may say "du" or "Sie"; it depends on the situation

Übung L: This exercise practices the accusative: the things that we "haben" or "nicht haben" are the objects of the verb "haben" and so in the accusative.  For neuter, feminine and plural nouns, that makes no difference to the form, but for masculine nouns, it means using "einEN" and "keinEN"  Remember in general for any verb except "sein" (and "heißen" and one or two others we'll see later):
--the person or thing doing the action is in the nominative (==>der/das/die/die) and the verb agrees with him/her/it in its ending.  It is called the "subject" of the verb.
--the person or thing "being verbed" is normally in the accusative (==> den/das/die/die) and is called the "direct object" of the verb.  

Übung O : The model uses "normal" time, but "military" time is of course fine too.   

Übung P : If you have a class at 1, that's "um ein Uhr"; NICHT "um eins Uhr."  

Übung W (the essay=der Aufsatz): You should normally stick to "du" consistently, and never switch back and forth between "du" and "Sie."  The "du" form is irregular for a number of simple verbs (like "sprechen"), as we'll see in Kapitel 3, but don't worry too much about this for now. A couple of forms that may be useful for this activity: fahren [=to drive] ==> du fährst, er/sie fährt; essen ==> du isst, er/sie isst; lesen ==> du liest, er/sie liest; sehen ==> du siehst, er/sie sieht; sprechen ==> du sprichst, er/sie spricht.