A.communication
B.instance
C.attention
D.signal

A.small
B.rude
C.slight
D.formal

A.clapped
B.nodded
C.shook
D.hold

A.head
B.hand
C.eye
D.ear

A.coming nearer to
B.catching sight of
C.pointing at
D.looking up to

A.on
B.to
C.at
D.for

A.greeted
B.thanked
C.congratulated
D.agreed

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.