Observation 1: The big parts of language are easy; the small parts are hard.
Observation 2: Mistakes are often more interesting than correct answers.
My students have just finished the textbook and today was a revision day before the test tomorrow. One revision question was something like “My father (watch/watches/watching) television every day”. Several students chose watch. This is, of course, incorrect standard English, but only by a twist of history. There’s no particular reason why third-person singular verb forms have –s/–es. There’s no possibility of misunderstanding. Many languages exist quite happily with the equivalent of “My father watch television every day”. Indeed, some non-standard varieties of English exist quite happily with exactly that. Nothing would be lost and quite a bit would be gained by omitting 3sg –s/-es, but standard English includes it, so that’s what I’ve got to teach and that’s what’s my students have to learn. (Several hundred years ago, standard English lost 2sg –est, and no-one missed it.)
A new student arrived late, and during the introductions one student said “I come Australia six month”. I almost understand what he meant. It could be “I came to Australia six months ago” or “I have come to Australia for six months” (that is, he’s in the middle of a six month stay). What’s missing is an irregular past simple verb, the prepositions to and for and the plural noun inflection –s.
One section of the revision focused on prepositions. Instead of giving students the choice of three, there was simply a space in the sentence. This produced sentences like “I have to look at my little sister”. Why not? It’s ‘correct’! (This reminds of a similar sentence in another textbook: “She has a job where she has to look ____ little children”. One student wrote for.) Another was “Wait ____ me. I’m almost ready.” Most students wrote for, but a few wrote with. For is certainly right, but with is not wrong, whether I’m in the same room as my wife and about to go down to the garage, or whether I’m half-way down the stairs.
In general, when two or more choices are given, sometimes one or more is just plain wrong according the rules of standard English grammar (eg must to and have to), and sometimes each is grammatically correct, but only one is possible in the context. I’m not convinced that putting grammatically incorrect choices in front of students is a wise thing to do. If they deliberately choose an incorrect choice, for whatever reason, then surely that is going to stick in their mind more than the correct choice, even if I tell them what the correct choice is in class (and explain, and give other examples) or on a corrected exam (which they rarely do anything more than skim over anyway). But if every question is a ‘fill the blank’, then the answer they write is more likely to stick in their mind. I’m not sure that there’s one perfect system here, so I can understand why textbook and test writers give a variety of formats.
Never Pure and Rarely Simple 