Which of the following sentences contains the nonessential expression? a. the airplane, circled once, and then came in for a landing. b. the mosquito bit me, and i have a huge welt on my arm. c. cabo san lucas, which is on the baja peninsula, is a fabulous place to visit. d. to win the game, we need a miracle.

C. Cabo San Lucas, which is on the Baja Peninsula, is a fabulous place to visit. 

Non-essential expression has nonessential elements such as word, phrase, or clause that are not important in the meaning of the sentence. Even if you eliminate that element, the meaning of the sentence won't change. 

Just like the statement found in letter C. The nonessential element here is "which is on the Baja Peninsula". This phrase only adds more information to the subject. Even if you omit this phrase, the meaning is still the same. 

A. The airplane circled once, and then came in for a landing. 
B. The mosquito bit me, and I have a huge welt on my arm.
D. To win the game, we need a miracle. 
  (All these three options have no nonessential element. All the words and phrases used are essential in completing the thought of the sentence.)

An inference that can be made is that the princess is bothered about the tiger door. although there are reasons for both this one has a better reason. the princess is not a monster and even if she didn't want to marry this man she wouldn't want him to die. the grudge of death is pretty heavy. unless she has done this before and feels no regret then she wouldn't want to be married to someone of low quality, if he is low quality.