There used to be a convention amongst Anglo-Saxon scientific journals that one never used the first person ("I" or "we") in a paper for publishing. The passive form was to be used to avoid this.

This is less the case these days and even "Nature" is not dogmatic on the point.
However, perhaps because the passive form in other languages is less frequent or clumsier than the active form, the first person tends to occur excessively in translated papers.

Even with the latitude granted by a more liberal minded scientific press it is still the case that papers originating from other languages frequently use the first person, particularly "we", to excess from the point of view of a native speaker.

Another means of avoiding "we" might be to use "one" like the French "on" but as this, in British English, is often used to parody the speech of the royal family who tend to favour that form of address it can now come over as mildly comic. Hence, to be avoided too.

Consequently, except when expressing the personal opinions of the writers, it is probably a good idea to favour the passive when writing or translating your paper.

The examples in this exercise are taken from papers for publication, the original sentence is given and all you have to do is to put the words in order (drag and drop) to make the corresponding passive version.

NB Some correct versions do not need every word and some versions would be improved with additional commas.