Which of the following is the correct si unit to use to measure length of a rope

You can use any unit you like when you're measuring the length
of the rope.

But if you ever want to write it down, memorize it, or tell other people
about it, then you'll want to convert your measurement into the unit
that gives you the most convenient number.

-- If it's a short rope, like one that just barely reaches across your bedroom,
then you'd want to describe its length in either centimeters or meters.

-- If it's a longer rope, like one that's coiled up on a reel and if you unwound
it then it could reach from your house to the main post office downtown, then
meters is probably the best unit to use.

-- If it's a rope on a reel that can reach from your house to the White House
in Washington when it's unwound, then you'd want to describe its length in
kilometers. 

B, if it was a lower watt she could put it in for her normal time and not burn it

The reflection of the candle in the concave mirror formed an upside-down virtual image that is smaller than the candle.in other words. the answer is the third option, c