Answer:
200 nm
Explanation:
We need a constructive interference to see the bright reflection
we know that
where m=1 and
is the wavelength of the gasoline
so 
putting the value of m and
in thickness equation

so the thickness of the film will be 200 nm
The answer you seek would be C. I just took this test C. was the correct answer
Answer:
Step 1 – Place Windows Vista DVD in your dvd-rom drive and start your PC. ...
Step 2 – The next screen allows you to setup your language, time and currency format, keyboard or input method. ...
Step 3 – The next screen allows you to install or repair Windows Vista.
Explanation: