ce is used with the verb être as follows: in its singular form, c'est, means it is /this is /that is, and in its plural form, ce sont, means they are /these are /those are.
Je vis dans une <u>maison</u> (house) avec un jardin, pas dans un appartement.
Hope this helps
The missing word is eat, or mangé
The whole sentence is M Corot a mangé des sandwich aux sardines
