Use of the data booklet is relevant to this question.

the approximate percentage composition of the atmosphere on four different planets is given in
the table below.

the density of a gas may be defined as the mass of 1 dm3
of the gas measured at s. t.p.

which mixture of gases has the greatest density?

planet major gases /
% by number of molecules
a jupiter h2 89.8, he 10.2
b neptune h2
80.0, he 19.0, ch4 1.0
c saturn h2 96.3, he 3.25, ch4 0.45
d uranus h2 82.5, he 15.2, ch4 2.3

the first phase of the government’s plan for settlement was building the transcontinental railroad. the railroad provided a way to bring settlers and manufactured goods west and ship their agricultural and mining produce east. the transcontinental railroad was an essential artery for rapid development of the frontier.

the second phase of the government’s plan was a liberal land distribution policy that made it possible for many people to homestead. with these two key elements—transportation and cheap land—the government rapidly achieved its goal of persuading people to move west, settle on farms, and push back the frontier.

the answer would be b).