Using live-cell fluorescence microscopy, researchers observed that a red fluorescent spot moved from the plasma membrane into the interior of target cells when red fluorescent dye-labeled HIV was added to the cells. What is the best conclusion from these observations?

A) The hypothesis that HIV enters the cell via fusion with the target cell plasma membrane is proved.
B) The hypothesis that HIV enters the cell via fusion with the target cell plasma membrane is not supported.
C) The hypothesis that HIV enters the cell via endocytosis is proved.
D) The hypothesis that HIV enters the cell via endocytosis is not supported.
E) Neither hypothesis is supported by these results.