The correct answer is C. viscosity.
You can check the viscosity of the brake-fluid with using a voltmeter. You can see that by using the voltmeter and read on it the volts, the bigger the voltage the bigger the moisture in brake-fluid, thus less viscosity.
Answer:
50 atoms have decayed during that time
Explanation:
The radioactive decay is represented as

Where N is the amount of radioactive element after a certain time period
N0 is the amount of radioactive element during the initial time period
X is the half life of the radioactive element
Substituting the given values in above equation, we get:
atoms
So, 50 atoms of carbon-14 remain are left after decaying for 5700 years.
Hence, atoms of carbon-14 that decay during 5700 years are 100-50 - 50