The most accurate statement among the options provided is:
**Beakers have liquid volume (ml) markings on the side of them; test tubes are unmarked.**
Here's a brief explanation regarding the other statements:
1. **Test tubes are better for transmitting liquids than beakers:** This is not accurate as beakers are designed for pouring and transferring liquids more effectively than test tubes.
2. **Beakers and test tubes both have round bottoms:** This is often untrue; while beakers usually have flat bottoms, test tubes typically have cylindrical shapes with round bottoms.
3. **Beakers can be held over flame; test tubes cannot:** This statement is misleading. While beakers can be used over a flame, test tubes can also be used over flames in certain contexts (e.g., in a Bunsen burner setup), but caution must be taken depending on the material of the test tube.
Therefore, the clearest and most accurate statement is the one about the volume markings.