There are 6 chemical elements represented by Li, Na, Mg, Rb, Cs, and Fr that are written on separate pieces paper. You randomly choose 3 elements, one
at a time, without replacement.

Find the probability that the third element is Na.

Enter the correct answer in the box.

Astudent is determining the influence of different types of food on the growth rate of spiders. she feeds one group of spiders two caterpillars twice a week. the other group received similarly-sized beetles twice a week. she records the amount of time required for individuals to reach sexual maturity. her hypothesis is that the spiders feeding on caterpillars will have a faster growth rate because caterpillars have a higher protein content compared to beetles. in this experiment, what is the dependent variable? spiders assigned to different feeding groups. time required to reach sexual maturity number of prey items fed twice a week. growth rates of each group.