Mike in Joe are talking about transport in the future.

B. What for? There are quite a few around.

A. Stars on American coins

B. The teaching of astronomy in state universities

A. Had they finished one project, they would have started working on the next.

B. Only if they had finished one project did they start working on the next.

A. We were on the verge of giving up hope when the rescue party arrived.

B. Had the rescue party not arrived, we wouldn't have given up hope.

A. Tennessee was the first state to use half dimes

B. Vermont and Kentucky joined the Union in 1794

A. Despite feeling ashamed, Jenifer lost her chance of promotion.

B. If only Jenifer has seized her chance of promotion.