What does はもってmean in this conversation?

Question

A: コートをもっていますか？
B: ええ、もっています。
A: じゃ、せびろももっていますか？
B: いいえ、せびろはもっていません。

Answer 1

This は (pronounced as wa) is the topic-marking particle. もって is the te-form of もつ, and is a part of もっていません ("(I) do not have").

In the last sentence, せびろ ("a suit") is the object of もっていません ("I don't have"), but は must be used instead of を, because せびろ is being contrasted with the previous topic (コート). If B said せびろをもっていません in this context, it would sound awfully unnatural to Japanese ears.

See also:

• Japanese with Anime - Contrastive wa
• Particle は replacing を - where does the stress lie?
• Why can は and を sometimes be used interchangeably?