The sentence indicates that the family's Christmas celebrations must not have changed much. This is hinted at by the use of "although." It might well have been the case that some aspects of their lives had changed. When it came to Christmas celebrations, it seems that things had continued to remain the same. Whenever something is "changeable," it is mutable. When it does not change, it is immutable. 

The contrast in this sentence is between the techniques that were now available and those that are said to be "well-known" and "tested." We really do not know if the new techniques are dangerous. All we know is that they are not so well known and have not gone through testing processes like the other treatments. This indicates that they are likely experimental drugs, meaning that they are still in the process of being tested—though they have not been through all the testing that the other drugs have been.

The contrast expressed in this sentence is between Bonaventure and Thomas being friends and them being foes. All of the other details just tell us a bit more about them. There is only one option that is synonymous with "foe", namely "adversary." The word comes from Latin roots literally meaning turned against—as though an adversary is "turned against" his or her foe in battle.  

Whenever we describe someone's writing as being "flowery," we are saying that it uses many words (often implying that it uses too many). Jennifer's writing style is contrasted to a flowery writing style. This means that she must be rather brief in her manner of self-expression. Whenever someone is "terse" in his or her manner of expressing himself or herself, that person uses few words. This is the only option that expresses this idea of being brief, so it is the best option among those provided.

The contrast in this sentence does not focus on Lulu being hungry. Instead, it contrasts her demeanor to the other dogs, which are full of energy and are very loud. She is "calm," just waiting for the food. Therefore, the best option is "mellow." Whenever something is "mellow" it is calm and not harsh. Even a food can be mellow if it is not harsh in character. Lulu's mellow attitude is quite the opposite of the other dogs described in the sentence.

Despite is the correct answer, as it means in spite of. All of these answer choices are conjunctions, but only "despite" matches the context of the sentence. "Through," "but," "after," and "if" would misconstrue the meaning of the sentence. 

The sentence compares one particular marathon runner to the other runners in the race. They stopped, but she did not. Therefore, she was "steadfast," which means firm and unwavering. None of the other potential answer choices make sense in the blank, so "steadfast" is the correct answer.