We want to know what was the error that Rosa make in this calculation. On this case, we multiply:
Where we put 4 decimal places as the first decimal number has 3 decimal digits, and the second one has 1.
On the calculation Rosa did, we see that she just put 3 decimal digits on his answer, and thus the mistake occurs because she placed the decimal point in the wrong place in Line 5.
The answer would be C.
