A scientist is observing a eukarotic cell and a prokaryotic cell. Which structure could she only observe in the eukaryotic cell?

A well defined nucleus and cell organelles.

Explanation:

Eukaryotic organisms are those organisms which have true nucleus or membrane around the nucleus in its cell. In eukaryotic cells organelles such as mitochondria, ribosome, lysosomes, endoplasmic reticulum, golgi bodies and vacuoles are present. In prokaryotic cell, all the activities are performed by a single cell while in eukaryotic cell, organelles are present which performs specific functions.

well we can't tell you because we cant see the time give a screen shot or something.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.