only thing that bugs me is the glass with straw...
I found 5 things I can criticise about it. 1st, as m1kclark said below me, specularity. then, the transparency of the glass: the upper part being thicker, I think it should be way more opaque. Then, the texture, still on the top of the glass: though the surface changes, the texture seems to be "flat", going from the lower to the upper part without bending at all (it should change angles several times). 4th, the shadow of the straw doesn't continue to the bottom of it, while it should be as dark, if not darker, as the rest of the straw inside the cup. And finally, it seems to float in the air, because it has no clearly visible contact with the glass...
apart from that, it's great!
One word: specularity.
The diffuse lighting is great, and reflective surfaces are pretty good, but your specular shading has got some serious problems. (FYI specular shading is the "shiny" parts of the margarita glasses, for example, where the material most brightly reflects the light source.) Now, dull paint and cloth have low, soft (blurry) specular reflections, while steel and glass have high, sharp specular reflections, and frequently the color of the specularity is different for different materials. It is clear to my eye that ALL of your materials have white specularity set to a high level and are moderately sharp. Pink plastic cups don't shine like that, for example.
I would make the pink plastic cup's specular shading a very low level, with a color a lighter pink than the base material, and set to a very soft reflection instead of a sharp specular reflection. Conversely, the specular shading on the margarita glasses should actually be (a) stronger, (b) sharper, and (c) slightly green-tinted. Get rid of specular shading altogether for the straw-cup-with-designs, and for the blue bottle in the back just reduce the specularity and keep all other settings.
Otherwise, you've got the making of a good still-life! The lighting and textures are right, and the design and placement of the objects is pleasing. I think you'll get a good grade.
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