Coherence means that every sentence in each paragraph, and each paragraph in an essay, flows smoothly from one point to the next. True or false?
That's a tricky question, because coherence means a couple of things, really. It is both a "systematic or logical connection or consistency" and "integration of diverse elements, relationships, or values" (Merriam-Webster). I think the answer would have to be true, because what you refer to is a systematic or logical connection, meaning that your reader can easily follow the progression of your ideas.
In an essay, though, coherence is a bit more. It means your argument is clear and well-constructed, consisting of various sub-arguments and clear evidence whose relevance (to your main claim) you clarify as you go.
This is the bit many students miss: just because an essay "flows," it is not necessarily coherent in this respect. Students will often write a paper "about" something without managing to write a paper that clearly argues for something.