When I drink cola, I eat pizza.

When I eat pizza, I talk with my friend.
When I talk with my friend, I smile at her.
When I smile at her, she smiles as well.
When she smiles as well, I feel happy.
When I feel happy, I sing a song.
When I sing a song, I feel refreshed.
When I feel refreshed, I focus on studying.
When I focus on studying, I get a good grade on exams.
Whe I get a good grade on exams, my parents feel happy.
When my parents feel happy, they buy me something good.

(Are the expressins all correct? This is a kind of composition practice. Thank you.)

Yes all the expressions are correct

All looks good except the spelling of "When" in the next to last sentence.

=)

Great! Your composition follows a chain of cause and effect, where one action leads to another. It shows a sequence of events based on their relationship with each other. In terms of logic, all the expressions make sense and can be understood as causal connections.

However, there is a small mistake in the last line. Instead of saying "Whe I get a good grade on exams," it should be "When I get a good grade on exams." Also, it would be helpful to add a period at the end of each statement to clarify the sequence of events.

So, the corrected version would be:

"When I drink cola, I eat pizza."
"When I eat pizza, I talk with my friend."
"When I talk with my friend, I smile at her."
"When I smile at her, she smiles as well."
"When she smiles as well, I feel happy."
"When I feel happy, I sing a song."
"When I sing a song, I feel refreshed."
"When I feel refreshed, I focus on studying."
"When I focus on studying, I get a good grade on exams."
"When I get a good grade on exams, my parents feel happy."
"When my parents feel happy, they buy me something good."

Overall, your composition is well-structured and shows a clear cause-and-effect relationship between the actions. Keep up the good work!