Option 1 is correct coz it follows closure, identity is 1, invere of every element exist and multiplication follows associativity.
Option 2 is also correct coz it follows closure, identity is 0, each element has inverse and associativity is applicable on addition.
Option 3 does not follows associativity.
Option 4 is a cyclic group i think....every cyclic group is abelian group and thus it is also a group.
