Answer:
d. frugal.. fluctuated.
Step-by-step explanation:
The term "frugal" refers to a person who is stingy, or economical about his/her spending. In other words, it means someone who is a spendthrift. Likewise, the term "fluctuate" refers to the change in things, be it a rise and fall, the swinging or oscillation of opinions or things.
Now, looking at the given passage, the word frugal will be used to describe the man who "saved every penny" so that he would become a millionaire. But despite this 'frugal' lifestyle, even the loss of his wife and family did not successfully fluctuate or change his life.
With that, the passage becomes-
For a long time, the frugal man saved every penny he earned with the plan of buying investments that would make him a millionaire. This lifestyle cost him his wife and family but despite this, his ideas never fluctuated.
Thus, the correct terms or words to use in the given passage is option d.