That's strange because it was clear to me (and others as noted above) that the answer was not 90 and then made perfect sense that it would be 60. You only say it wasn't clear because you missed it. I don't see you complaining about any of the questions you got correct.
it can't be 60 minutes muzikool
even in the best case scenario where we took his question the way he wants to believe it should be interpreted (which is not the way a prescription should be read, more later), his answer is till incorrect if we take it his way
the time in his scenario would still have to be a fraction of a second more then 60 minutes at the very least, it couldn't possibly be 60 minutes
if the multiple choice read "as little as 60 minutes pus a fraction, and as much as just under 90 minutes by that same fraction" that might be the correct choice given his interperatation...in any event the "answer" he listed not possible and it's incorrect
so, even though he's wrong regardless I'll give you two practical example which will show that you don't use his interpretation when it comes to a doctors prescription
if a doctor said "take this after your meals" that would definitely not mean after your previous meal it means after your next meal.
if the doctor wanted you to take it now he would say "take one now and then every half hour"
and now the more important practical example;
some drugs, like certain antibiotics are important to amass, a little at a time won't be affective and they have to accumulate
the protocol of taking this type of antibiotic would not indicate you take the first one immediately it indicates they need to be taken in sequence
now, if the doctor said "take these every hour till they are gone " that would in no way mean take it now, in fact you better not take it now if you can't follow the protocol of taking it every hour, you better wait until you are certain you can take it every hour
same exact thing and this authors answer is wrong
and as I said before, even if the assumption of the author makes is correct, then when the doctor said "every half hour" that couldn't possibly "start now" could it, the clock would run beginning any time from now and a half hour from now and it would take time to take that first pill from when the prescription were first given...I would think at least a few seconds unless he threw the pill into your mouth as he was giving you the prescription
not likely