$1.$ On Christmas day, Mark usually goes to his parent's house.

→ Câu nhận biết: On Christmas day, I usually go to my parents' house.

Dấu hiệu nhận biết thì hiện tại đơn: usually (thường xuyên)

Công thức thì HTĐ với động từ thường: S + Vs/es + O

$2.$ This Christmas, he is visiting his friends and now, he is having a barbecue next to the swimming pool.

→ Câu nhận biết: I'm in Australia. I'm visiting friends. This morning I went to church, and now I'm having a barbecue next to the swimming pool. 

Thì hiện tại tiếp diễn: S + is/ am/ are + V-ing + O

Dùng để diễn tả một sự việc đang diễn ra ngay tại thời điểm nói.

1 : He usually goes to his parents' house , opens his present , then has a big lunchn at about 2.00 in the afternoon

Thông tin dòng : 2 ; 3 

Chỗ : On christmast -> In the afternoon 

2 : He is visiting friends and now He is having a barbecue next to the swimming pool

Chỗ : : I 'am visiting friend 

chỗ : And now , I'm having a barbecue next to the swimming pool and wearing a swimsuits