What is the distinguishing feature of the limited partnership?

Question

(a)The partners run the business together and share all profits and losses according to the partnership agreement.
(b)The partners have liabilities limited to their personal assets only.
(c)Some partners are involved as investors while other partners manage every day operations.
(d)The partners have their investments protected from the creditors; however, they are liable for up to the amount of
their assets.
(e)The partners can elect the board of directors that selects the managers to run the business in the interest of the
partners.

I answered (b) on my test, but my teacher marked it wrong. I'm now confused about this. Any help would be appreciated.