A.\(\frac{R}{{\sqrt {{R^2} + Z_C^2} }}\)
B.\(\frac{{\sqrt {{R^2} + Z_C^2} }}{R}\)  
C.\(\frac{{\sqrt {\left| {{R^2} - Z_C^2} \right|} }}{R}\)  
D.\(\frac{R}{{\sqrt {\left| {{R^2} - Z_C^2} \right|} }}\)

A.Mĩ.
B.Pháp.
C.Anh.
D.Liên Xô.

A.Russian cosmonaut Yuri Gagarin was the first man to fly to space in April 1961.
B.The longest time spent in space by an astronaut is a year.
C.Most astronauts encounter short-lived or long-lasting physical issues.
D.Astronauts have to pay their full attention when travelling in space.

A.dedication
B.robots
C.people
D.astronauts

A.Being able to easily blend with people
B.The ability to travel a long distance
C.Being able to regulate his or her emotions
D.The competence to act in different situations

A.delivered
B.dissolved
C.separated
D.removed

A.The first man on Mars
B.Human adaptation to space
C.What makes a good astronaut?
D.Difficulties encountered by Yuri Gagarin

A.The first man on Mars
B.Human adaptation to space
C.What makes a good astronaut?
D.Difficulties encountered by Yuri Gagarin

A.higher
B.bigger
C.greater
D.larger

A.who
B.when
C.that
D.whose