El unico que se es el del oxígeno: o2
Answer:
Up first are Mercury and Venus. Neither of them has a moon. Because Mercury is so close to the Sun and its gravity, it wouldn't be able to hold on to its own moon. Any moon would most likely crash into Mercury or maybe go into orbit around the Sun and eventually get pulled into it.
The answer would be machines
Answer:
A longitudinal study is a research design that involves repeated observations of the same variables over short or long periods of time. It is often a type of observational study, although they can also be structured as longitudinal randomized experiments.
Explanation: