Parallel structure is the use of the same grammatical structure when listing or comparing items. Using parallel structure helps to show the reader that the speaker is making a relationship between or among the items. In the first question the sentence starts with the structure "Videos that have people". The author then compares this to "only landscapes". The author is trying to create a comparison between these two things so the grammatical structure should be the same. This means "videos that have only landscapes" is correct.
The second question has two sets of items that need to have parallel structure. The first uses the verb "practice" as a gerund so the next verb needs to be written in gerund form as well. This makes "performing" the correct choice. In the second set of items the simple present form of the verb is used for the first item. This means the second item also needs the simple present form - develop.
Child labour refers to the exploitation of children through any form of work that deprives children of their childhood, interferes with their ability to attend regular school, and is mentally, physically, socially and morally harmful.
