What UNITS will be used for Thermal and Fluids Systems PE

Hello I will appear the PE exam in October 2018 in Thermal and Fluid Systems. I have a question regarding UNITS.

Guideline says "The exam uses both the International System of units (SI) and the U.S. Customary System (USCS)." 

What does it mean?

1) Does this mean that in same question will have USCS and SI unit? 

2) Or total exam will use USCS and SI unit, but some question will be SI unit and some are in USCS unit

Which one is correct? 1 or 2?

Both 1 & 2 are correct. 

A problem may have data in US customary units and they may ask you to answer in SI.

I have been using the unit conversions book by Lindeburg while studying. It has been very useful while working problems and a time saver. 

McEng said:

I have been using the unit conversions book by Lindeburg while studying. It has been very useful while working problems and a time saver. 

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That book is great. Highly recommended.