Definition: Given the Question and Answer pair, detect whether the answer is acceptable or not. Denote acceptable answer as "yes", otherwise denote as "no". An acceptable answer is consistent with the context in question, detailed, long, and uses general knowledge of English. Answers that are not definite and suggest a variety of options are not acceptable answers.
Input: Question: Does the letter 'C' make any sound that cannot be made by other letters? "Cat" could be spelled "Kat," "Cinder" could be spelled "Sinder," and "Watch" could be spelled "Watsh." Edit: An excerpt from a comment by Kosmonaut: There is no difference between ["ch" and "tch"]; both are /t/. Thus, "witch" and "which" are pronounced exactly the same: [wt]. (Actually some Southern American dialects pronounce "which" as [t], but that is only a difference in the "w" sound, not the /t/.) 
Answer: You've answered youself. Ch creates - among other pronunciations of this digraph - the sound tsh' which cannot be created otherwise. Like cheese, China and lots of other words. Sometimes it's used with t before, like in watch, scotch thus putting more stress on the t part of the sound.

no