Kind of we tried to avoid similar expressions in a written language, we anyway all the same face them and again we ask a question: how to write? Together or separately? On the end of E or I? And why so, but not differently what it depends on? Some adverbs and pretexts just need to be remembered, and in certain cases it is necessary to understand at first whether an adverb it or the noun with a pretext, will depend on it also writing.
Instruction
1. In a case with the word "current" it is necessary to define what it is about. If in the offer it is told about a watercourse, then in this case "during" is the pretext and a noun of a neutral gender standing in a prepositional or accusative case, answering the question "where?" or "where". Then it is necessary to write "in the course of the river" (on the question "where?") and "during the river" (on the question "where?"). If it is about time frames, then this phrase is an adverb and is written always "during": within one year, within a day.
2. The same happens to phrases "in conclusion", "in the investigation", "throughout". Remember that between a pretext and a noun it is always possible to insert some adjective, for example, "in a rapid current of the river" whereas the adverb is uniform even if it is written separately. Compare: In (this) investigation there are a lot of white spots. Thereof business will not be closed for a long time. In conclusion he told that he was glad all to see. He stayed in (prison) conclusion within two years. Throughout told I will note that it is not a limit. In continuation to the book you learn, than this story ended.
3. There are still phrases which writing depends on a context. Compare: I not it had money for (bank) account. We did not want to go on (this) meeting. They met halfway each other.
4. Remember words which are always written only this way and in any way differently: "subsequently", "like", "the day before". Are always written separately: "unlike", "in communication", "in force", "on a measure".