11.Throughout the passage,the author implies that the Mandans
(A)planned for the future
(B)valued individuality
(C)were open to strangers
(D)were very adventurous
Questions 12-20
However,when the universe was less than one minute old,no helium could have existed.Calculations indicate that before this time temperatures were too high and particles of matter were moving around much too rapidly.It was only after the one-minute point that helium could exist.By this time,the universe had cooled sufficiently that neutrons and protons could stick together.But the nuclear reactions that led to the formation of helium went on for only a relatively short time.By the time the universe was a few minutes old,helium production had effectively ceased.
12.what does the passage mainly explain?
(A)How stars produce energy
(B)The difference between helium and hydrogen
(C)When most of the helium in the universe was formed
(D)Why hydrogen is abundant
13.According to the passage,helium is
(A)the second-most abundant element in the universe
(B)difficult to detect
(C)the oldest element in the universe
(D)the most prevalent element in quasars
