Mitochondria and chloroplasts have a number of features in common. which of the following is not one of them? (a: both are surrounded by a double membrane; b: both are important to energy conversion; c: both are found in all eukaryotic cells)

The best answer is C.

Chloroplasts are not found in all eukaryotic cells but only in plant cells. Animal cells are eukaryotic in nature but animals do not have chloroplasts in their cells because they do not engage in photosynthesis.

Photosynthesis is the process by which plants make their own food. Chloroplasts  contain chlorophyll which is essential in t trapping sunlight from which supplies the energy for photosynthesis. 

Animals do not make their own food like plants but eat ready made food so their cells  lack mechanisms for food manufacture.

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]