A.\(\dfrac{{a\sqrt 2 }}{2}\)
B.\(2a\)
C.\(\dfrac{{a\sqrt {15} }}{5}\)
D.\(\dfrac{{a\sqrt 7 }}{7}\)

A.Tam giác \(ABD\) là tam giác đều.
B.Bốn điểm \(A,\,\,B,\,\,C,\,\,D\) tạo thành tứ diện.
C.\(AB\) vuông góc với \(CD\).
D.Tam giác \(BCD\) là tam giác vuông.

A.the figurative meanings of the word culture
B.the distinction between culture and civilization
C.the derivatives of the word culture
D.the multiplicity of meanings of the word culture

A.the figurative meanings of the word culture
B.the distinction between culture and civilization
C.the derivatives of the word culture
D.the multiplicity of meanings of the word culture

A.qualities
B.skills
C.aspects
D.fields

A.comes from a source that has not been identified
B.develops from Greek and Roman literature and history
C.is related to the preparation and use of land for farming
D.derives from the same root as civilization does

A.regular
B.dense
C.balanced
D.unchanged

A.Cultures
B.Developments
C.Evolutions
D.Conceptions

A.The use of the word culture has been changed since the 19th century.
B.Distinctions have been drawn between culture and civilization.
C.The word culture can be used to refer to a whole way of life of people.
D.Anthropology and sociology have tried to limit the references to culture.

A.classical literature, philosophy, and history have not been taught as compulsory subjects
B.all schools and universities have taught classical literature, philosophy, and history
C.schools and universities have not taught classical literature, philosophy, and history
D.classical literature, philosophy, and history have been considered as core subjects