The correct answer is B. Despite
Step-by-step explanation:
In grammar and sentences most of the words that show the way different elements in sentences are related or connected are transition words such as moreover, however, additionally; conjunctions such as and or but; and some prepositions such as before, besides, except and despite. Additionally, the type of word in a sentence that indicated relationship varies according to the meaning of it. In the case of the sentence "Despite our best efforts as parents, we will always make mistakes in raising our children", the main point or meaning is that the efforts parents do are not enough for avoiding mistakes when raising children, this implies the word that indicates the relationship between "our best efforts as parents" and "we will always make mistakes in raising our children" is the word "despite" as this is the word that determines the sense in the sentence and this word is also a preposition which is a type of word commonly used for this purpose. Thus, the word in the sentence that indicates a relationship is the word "Despite".