【正确答案】In sentence (a), the word "cremains", formed after blending "cremation and remains", means the ashes that remain after the cremation of a corpse. Blending is typically accomplished by taking only the beginning of one word and joining it to the end of the other word. If you combine smoke and fog, there's the term smog.
In sentence (b), "upper" and "downer" are formed after adding the derivational morpheme "-er". Derivation is accomplished by means of a large number of small "bits" of the English language which are not usually given separate listings in dictionaries. For example, if you add "-un" to "happy", you will get "unhappy".

【答案解析】[解析] 本题考查构词方法，考生应熟知发明、借词、混合、合成、派生、曲折、逆构、缩略等构词方法。