○　正解です。

People say 'Come in' (いらっしゃいどうぞ) when they want somebody to enter their house.
'Make yourself at home'(気楽にしてください) means you want the other person to relax and feel like they are in their own home.

'Can I help you?' (いらっしゃいませ) is a greeting used by staff in shops.

If you want to offer your guest a seat you should say 'Have a seat'.