Fill in the blank to use names from std namespace: ------------ namespace---------

Question

I don't know it
please help me

Answer 1

you can click back in the lessons with no penalty to look at the previous slide again

Answer 2

using namespace std;

Answer 3

Yeah looking back doesn't deduct XP, only using hints or unlocking answers does

Answer 4

using namespace std;

Answer 5

Fill in the blank to use names from std namespace: ------------ namespace---------

I don't know it
please help me