Составить предложение на британском из слов they/ lights/ the/ are/ on/

1). They must be at home because the lights are on. - Они обязаны быть дома, поэтому что пламенеет свет.

Complex sentence, which refers to the present tense.  The first part is the assumption, and the second one is the grounds for it.

2). I am sure but you could be right. - Я уверен, но вы сможете быть правы.

Complex sentence. Complex sentence, which refers to the present tense. The first part is the statement of confidence, and the second one is the assumption that the opinion can be wrong.