"measures to the nearest tenth of a pound" tell us to round each of the weights listed to the nearest tenth (since the unit is already pounds, no conversion is needed). What this means is if the second number to the right of the decimal is 5 or greater, then we add 1 to the first number to the right of the decimal (and replace the second number with a zero). With all this said, it's much easier to show you, rather than to try to explain it. :D
4.35 is rounded up to 4.4 because the second number to the right of the decimal is 5.
Packet A = 4.4
Packet B = 4.4
Packet C = 4.5
Packed D = 4.4
The question is asking what the heaviest reading will be, so from the whole list above we pick the highest number which is 4.5 pounds. Notice how the answer is not Packet C, or 4.48 pounds, but 4.5 pounds. It is asking for the reading, not the packet, nor the weight. Hope this helps.