# Tutor profile: Logan H.

## Questions

### Subject: SAT

Which word in this following passage is incorrect? (Word is followed by choice letter in parentheses.) "Peter's (A) children had nowhere to wash their (B) clothes, so they grew dour (C). All the other parent's (D) children laughed at Peter's children." (E is "none of the above")

The correct answer is D. For choice A, the children are Peter's, therefore the possessive is appropriate. For choice B,. "their" is correct, rather than "they're" or "there". For choice C, the uncommon word "dour" is properly used. In choice D, using "parents'" instead of "parent's" is appropriate, because there are multiple parents.

### Subject: Linear Algebra

What does "one-to-one" mean?

A linear transformation being "one-to-one" implies that for every possible input vector, there exists exactly one output vector. In this way, information is preserved through the transformation -- there are exactly the same number of vectors in the input space as in the output range of the linear transformation.

### Subject: Java Programming

I want to store a large number of unique grocery items, then print them in alphabetical order. What data structure should I use?

Use a TreeSet! This class is a Set, therefore it maintains uniqueness. Because it is a TreeSet specifically, it automatically maintains an order to the elements, making it easy and efficient to retrieve them in alphabetical order. If you want to know more about why this is, just ask.

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