"It is totally childish."

My grammar book tells me that when an adverb modifies another adverb or an adjective, it usually precedes the word it modifies. Here "totally" is modifying an adjective, "childish," so "totalmente infantil."

What's wrong with it? It's too childish to say that.

But is a description of something. Entonces se usa SER.

Ya... That's exactly what I thought. So why not estar?

If you are familiar with the acronyms PLACE and DOCTOR for estar and ser respectively you will find that most of the more advanced issues of the use of estar and ser come from the difference between the C in each. Is it a condition or characteristic. In this case he is a childish person (characteristic) Sometime you can argue it both ways even under the same circumstances. In those cases you just have to learn how Spanish views it. But from a post above I saw someone say that if you returned from an animated argument with a friend you might say of that friend, está loco (at least colloquially). So for this case a good way to remember the difference is to think of es loco as he is crazy and está loco as he is ACTING crazy. But more universally that he was in a crazy condition.

For this question, they want you to demonstrate your knowledge of the word "totalmente" rather than "muy". I am not sure about "juvenil" versus "infantil".

Yes. Childish Ness is a characteristic not a condition so it uses ser. That is true both for it or he/she.

Conversationally, that would be perfectly correct to say, but in learning, these programs want you to distinguish between "it" and "that".

Ribeiro and wolofka: eso = that; esto = this. You are introducing something else into the sentence. What do you mean "the one-to-one word translation rule"??? What rule is that? It sounds a recipe for disaster! For example, it seems to have led you, wolofka, to forget that the one word "es" can translate as the two words "it is" (and in fact does if no other subject there or no context to assume it means "he is" or "she is") and I think both of you inserted the unnecessary eso/est o becaus eyou were trying to have an explicit subject.

Esto es means this is. DL wanted us to translate it is.

The worst idea people ever make is growing up.

Lo is the direct object pronoun, not the subject pronoun, although there are a couple of idiomatic expressions where it appears more as if it were. Spanish does not have a pronoun for this amorphous "it", and will always just use the third person singular congratulation without a pronoun. Spanish deals differently with these amorphous ideas. Remember it has a special word just to say "there is/there are, and a different form for this and that when the referent does not tie back to a concrete noun. But for this situation it simply takes advantage of the ability to drop the pronoun totally.

Read Lynette response. This would be more like a response though. If someone were to ask you is it chidldish? You could answer Lo es...

That would be This is totally childish. One of the reasons for this question is to underline the fact that Spanish has no it subject pronoun. While all subject pronouns may be omitted, this type of neuter it statement will never have a subject shown.

"Esto" means "this". You can leave out "esto".

I went with "inmaduro" (not on theoretical grounds...I just couldn't come up with "infantil" at the moment). Marked wrong. Reported for the heck of it.

It is still in use today.
By the way, the Spanish "pueril" also derives from Latin, and is accepted by DL..

In La casa blanca, the adjective blanca comes after the noun it modifies which is Casa. In this sentence infantil is a predicate adjective modifying the subject It and totalmente is an adverb. Adverbs which modify verbs have some options in syntax, but adverbs modifying adjectives ALWAYS precede the adjective it modifies. There are cases where adjectives also precede the noun, but they obviously don't apply here.

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