Normal subgroup

Which of the following is always a normal subgroup of a group G ?

• The centre of G

• Any subgroup of G

• Any cyclic subgroup of G

A subgroup H of a group G is called normal if:

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• H = G.

Which of the following statement is true?

• Every sub group of a group is normal

• Every sub group of an abelian group is normal

• Only cyclic sub group are normal

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• Form a ring

• Forms a field

• Forms a groups.

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