Answer :
The answer to the question above is letter "D. 4". The number 1.050 has four significant figures because for the number with decimal point, we start counting the number of sig fig from the left. Thus, the first significant figure is 1. All the numbers including zero which come after this number are considered significant.
The measurement given in the question is 1.050 L. It has to be understood that all numbers on the right side of a decimal, including zero are significant numbers. Also any number above zero on the right side of decimal is significant number. So in this measurement there are 4 significant numbers. The correct option among all the options given in the question is the last option or option "D".