if you measure a 5cm line with a ruler that is marked off in 0.1 cms, how many digits should the measurement have?

3 digits .

Explanation:

The least count of the ruler that is being used is 0.1 cm , hence it can measure upto one decimal point of cm . One more decimal point can be inferred .

So the measurement of 5 cm will look like

5 .00 cm or it will have 3 significant figure . The last figure of the measurement suffers from error as it has been inferred or guessed.

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.

i believe the answer would be:

d. violin, clarinet, french horn, and tuba