Answer:
neglected by another
AND
to fall into decay
Explanation:
Thriftless implies when a person is spending money in a way regarded as wasteful or extravagant. From the passage, thriftless as used signifies a heir who spends money built by his father recklessly, hence the words from the text that helps to indicate the meaning of the word as used in the passage will be "neglected by another" and "to fall into decay". These shows thriftless and a nonchalant attitude towards money being spent or already spent.
Your answer is A) Humble
Hope this helps. Have a nice day/weekend.