Grammar

I need to take a Diagnostic English Test (DET), because I am not undergraduate from Singapore. I had to be at least Band 3, to be exempted from taking extra English course for my post graduate study in NUS. Unfortunately, I got a Band 2, so I need to take ES5001A (Graduate English Course) for this semester.

The course is about Academic Writing. The lecturer is Dr.Halim, a Britain. After several classes, I found the key reason why I can not pass for DET test. The course helps a lot, especially for people like me who seldom read English novel and first language is not English. I never have a proper English class like this, and I really appreciate it. I will describe more interesting events in the class later, but today I wish to share a simple question.

For 4 sentences below, which is grammatically incorrect?
1. Many papers are published in English now,
2. Now many papers are published in English.
3. Many papers now are published in English.
4. Many papers are now published in English.

I will come back to this.