Which expression is written in proper scientific notation?

A time interval of 2000 microseconds is equal to:

When a decimal point is moved to the right to write a small number in scientific notation, the exponent is:

Which prefix represents 10^-9?

Before adding two quantities written in scientific notation, their powers of ten should be:

Which derived unit is equivalent to metre per second?

Which is the correct SI symbol for second?

Which SI base unit and symbol are correctly matched?

Which unit symbol is correctly capitalized because it is named after a scientist?

Which of the following is a complete measurement?

Why were standard units introduced?