"The boys sleep on a small bed."
Translation:Los niños duermen en una cama pequeña.
‘sobre’ means “on” only in the sense of “on top of”, whereas ‘en’ has a more general meaning ranging all the way from “on top of” to “inside”. If the boys are sleeping on a bed of nails, either ‘sobre’ or ‘en’ would be appropriate, but ‘sobre’ doesn't apply for an ordinary bed unless they're sleeping on top of the bedding.
I agree. The odd thing here is the English version (which I was given to translate). The English uses "on." If the boys were in the bed, in English I would say, "The boys sleep in...etc." The use of "on" is slightly odd and implies they are not actually "tucked in." :) They are on the blankets or whatever, or they fell asleep while playing on the bed, etc. So I avoided "en" and used "sobre." Such is the slippery nature of language!
Well, even in English, many people differentiate between "on" the bed (as in "put it on [top of] the bed [covers and everything]) and "in" the bed (as in the phrase "get in bed [under the covers]") just like there seems to be a difference in Spanish.
No one tells a child to "get on (the) bed" at bedtime. We say "go to bed" or "get in bed". Nor would someone say "Oh, they are on the bed" in response to "where are the kids?" unless the respondent literally meant that they are on the bed playing or something. I think it's just a poorly worded phrase/translation into English from Spanish.
In Spanish, unlike in English, an adjective can occur either before or after a noun, but the choice affects the meaning. As a rule, the ‘topic’, or old information, comes first in a Spanish sentence, and the ‘focus’, or new information, comes last, as in most languages, including English.
Sleeping in a bed is ordinarily expected; what's unexpected —the new information— in this situation is the smallness, so the adjective ‘pequeña’ comes last: ‘Los niños duermen en una cama pequeña.’.
‘Los niños duermen en una pequeña cama.’ would make sense if it were the bed that's unexpected, not the smallness; for example, if the listener thought they boys sleep in a hammock or a rowboat.
As another example, the sentence ‘En una pequeña cama duermen los niños.’ implies that the boys are what's unexpected.
Another way of looking at it is that the adjective in ‘cama pequeña’ restricts the set of beds the sentence might be referring to, by excluding larger beds; whereas in ‘pequeña cama’, the adjective is non-restrictive, just a comment.
Probably when speaking generally, as 'cot' can replace 'small bed', although there is a difference between those two. [A small bed is not necessarily a cot.] However as the exercise is designed to learn and practice specific 'size' words such as 'pequeña', here you would be required to write 'small bed' translated literally from 'cama pequeña'.