COMMON PROBLEMS You chose text B... In text B, the links connecting sentences are between comments rather than between topics. This makes it appear that the writer is not discussing one topic, but rather jumping around between many. This can be confusing at the least, and presents the readers with a difficult reading challenge. TOPIC COMMENT Ion exchange is a process in which ions bound to a solid-state compound are exchanged for ions in a surrounding solution. Specific substances can be removed from an effluent by this process. Distillation has, in many places, been superseded by ion-exchange processes, which are a fast and energy-efficient means of water purification.   In text A, the information content is the same, but the 'given' information that creates links between sentences ('the ion-exchange process') is placed in 'topic position'. This makes it easier for the readers to understand what the text is about. TOPIC COMMENT Ion exchange is a process in which ions bound to a solid-state compound are exchanged for ions in a surrounding solution. This process can be used to remove specific substances from an effluent. Ion-exchange processes have, in many places, replaced distillation as a fast and energy-efficient means of water purification. Therefore, what have we learned from all of this? To make it easier for readers to understand what the text is about, writers should limit the number of different topics introduced within a single paragraph. This helps to guarantee a sense of unity, 'coherence', in your text.

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