b. simple sentence
Verbs are basically action words. You can easily spot them in a sentence if you look for words the show movement or state. For example, in the sentence: A mammal's body takes the ingredients from the blood supply and changes them into milk, the words that denote action are (a) takes and (d) changes. Moreover, these are transitive verbs. Transitive verbs need objects to complete its meaning. Hence, "takes the ingredients" and "change them".
The word (b) from is a preposition. The word (c) body is a noun.
