I'm a 16 year old from belgium, and last week we had an english test.<br/><br/>We had to make a sentence with the word reinforce<br/><br/>So I wrote: We have to reinforce the castle walls at all cost.<br/><br/>Now: my english teacher, who I think is a real BIATCH btw gave me a 0.5 on that sentence because she said it had to be "At all costS") with an S<br/><br/>Though i'm not sure I think my sentence is correct.<br/><br/>Help is appreciated.