mong anh chị giải thich cho em khi nào bỏ dấu

phẩy , khi nào không ? nếu có thiếu dấu thi bỏ

vào dùm em, xin anh chị giải thích các cặp a và b cho em hiểu nó khác nhau như thế nào? . thank you very much
1 the S.S. Titan is a supertanker. it crashed into a cargo ship

1a) the S.S. titan which is a suppertanker crashed into a cargo ship

B )Tom's father goes swimming everyday . Tom's father is 78

Tom's father who is 78 goes swimming everyday

2a)Ms . Laine lost her house. she is sleeping in a hotel

Ms . laine who lost her is sleeping in a hotel

B)the clock was Mary's . it stopped running

the clock which stopped running was mary's

3a) the temperature will be low today. it will rise tomorrow

the temperature which will be low today will rise tomorrow

B) people drink a lot of tea. they live in vietnam

people who live in vietnam drink alot of tea

4a) the house was on the edge of a cliff . it fell into the ocean

the house which was on the edge of a cliff fell into the ocean

B) she showed me a photograph of her son .her son is a policeman

she showed me a photograph of her son who is a policeman

5a ) the van belonged to the sandiego zoo. It contained two boxes of snakes

the van which belonged to the sandiego zoo contained two boxes of snakes

B ) the new stadium will be opened next month . the stadium holds 90.000 people

the new stadium which holds 90.000 will be opened next month

6a) the local residents are spending the night in a school . they are afraid to go home

the local who are resident are spending the night in a school are afraid to go home

B) the population of HCM city is more inbcreasing . HCM city is the largest city in Vietnam

the population of HCM city which is the largest city in Vietnam is more in creasing

7 )john is one of my closest friend . I have known john for eight years

john who I have known for eight years is one of my closest friend

8) the rice is very good . it grows in vietnam

the rice which grows in vietnam is very good

9) the postman was late this morning . the postman is nearly always on time

the postman who is nearly always on time was late this morning

10) a city has many problems . it grows very rapidly

a city which grows very rapidly has many problems