Grammar Editing

What is the best way to rewrite these sentences? Sarah was great at math. Sarah was not very good at writing. 

• Sarah was great at math but she was not. Very good at writing. 
• Sarah was great at math. But not good at writing. 
• Sarah was great at math, but she was not very good at writing. 
• Sarah was great at math but she was not very good at writing. 

What change if any should be made to this sentence?
"Can we go to the park later today? asked Todd. 

• Change the question mark to a period
• Changed asked to Asked
• Insert quotation marks after today
• Make no change

What change if any should be made to this sentence?
The teacher said to the class, I hope they're having a good time today."

• Change they're to their
• Insert quotation marks after class
• Delete the comma after class
• Make no change

What change if any should be made to this sentence? 
I wonder if its their birthday today. 

• Change its to it's
• Change their to they're
• Change wonder to wunder
• Make no change

What change if any should be made to this sentence? 
Yesterday we build a fort at recess.  

• Chance recess to resess
• Change build to built
• Insert a comma after build 
• Make no change

What change if any should be made to this sentence? 
"I really hope you can come to my party this weekend," Said Peggy. 

• Change the comma to a period after weekend
• Change Said to said
• Insert a comma after party
• Make no change

What change if any should be made to this sentence? 
"We should probaly leave for the movie soon," said Bob. 

• Change the comma to a period
• Change said to Said
• Change probaly to probably
• Make no change

What change if any should be made to this sentence? 
Ive already reserved a spot on my shelf where I can put my trophy. 

• Change Ive to I've
• Change already to allready
• Change where to were 
• Make no change

What change if any should be made to this sentence? 
If your good at math then you will love this new game. 

• Change new to knew
• Change then to than
• Change your to you're
• Make no change

Which sentences are written correctly. 

• If we had a rock-climbing wall on our playground, it could also be used for PE classes.
• We could have a rock-climbing wall on our playground. Which could also be used for PE classes.
• We could have a rock-climbing wall on our playground, it could also be used for PE classes.
• If we had a rock-climbing wall on our playground. It could also be used for PE classes.