The correct response is: Plant cells due to the observation of chloroplasts.
This identification is based on the presence of chloroplasts, which are organelles found specifically in plant cells (and some algae) that are responsible for photosynthesis. The observation of mitochondria and ribosomes is not exclusive to plant cells, as these organelles are also found in animal cells. However, the presence of chloroplasts clearly indicates that the cells being observed are plant cells.