Final answer:
To round off 0.003456 to two significant figures, identify the first two non-zero digits, which are 3 and 4. Considering the next digit is 5, round up the second figure to 5, resulting in 0.0035.
Step-by-step explanation:
To round off the number 0.003456 to two significant figures, we need to identify the first two non-zero digits, since these will be the significant figures we'll keep. The number begins with three zeros, which are not significant, so the first two non-zero digits are 3 and 4.
Now, we look at the digit following the second significant figure, which is a 5. According to the rules of rounding, if this digit is 5 or greater, we round up the second significant figure. Since it is 5, we round the 4 up to 5. Thus, the number 0.003456 rounded to two significant figures is 0.0035. The correct answer is option (a).