Okay, so I SUCK at the end of chapter quizzes. I commonly get percentages in the high 60's, although do feel that I understand the material well and 99.9% of the time, I can see what I did wrong. How reflective are these (the end of chapter quizzes specifically) of your performance on the actual MCAT and/or the full-lengths? Should I be worried?

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Apparently, I can not read because I am scoring only about 50% on the topical and sectional tests. My test is in July and I have been studying forever with no improvement.

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I signed up for the Kaplan online course to get access to the online materials and I must say that the topical tests are extremely difficult and they make you think, much like the real MCAT - I find it more useful than my first run through with EK and AAMC tests. I don't know, I feel as of now that Kaplan's MCAT online course is so much more useful than what I found with EK, maybe because now I know how to study for this beast or Kaplan is better? I don't know...

I stumbled on question 2 in the end of the chapter practice questions and I looked at the explanation on the following page but I still don't get it.

Here's the question:
A child is practicing the second harmonic on his clarinet. If his brother covers one end of the clarinet for a brief second, how will the sound change?

This is how I went about trying to solve the question.
1. Clarinet has one open end and one close end (physical barrier of the mouth) so it's wavelength will be 4/3 L .
2. Now when the brother covers the open end its wavelength will be L.
3. Going from 4/3L to L the wavelength is decreasing so the frequency will be increasing. Hence, the pitch will be higher.

However, the explanation in the book says that wavelength increases from L to 4/3L. Are they considering the clarinet as an open pipe and then when the brother covers one end it becomes a close pipe?

Any clarification will be appreciated.

Yep, when the brother is playing the 2nd harmonic, it's a pipe open at both ends with λ = L. When the brother closes off one end, it's a pipe closed at one end with the 3rd harmonic, so λ = 4L/3.

Thanks, for the clarification. I was confused because in the chapter they mention that a clarinet should be considered a closed pipe!