All stable atoms are made of
-positively charged, with the number of protons exceeding the number of electrons
-negatively charged, with the number of electrons exceeding the number of protons
-neutral, with the number of protons equaling the number of electrons
-neutral, with the number of protons equaling the number of electrons, which is equal to the number of neutron

1. D. Charge-to-mass ratio of electrons was the same, regardless of the gas used.  

2. Millikan

3. A. 1/840 the mass of a hydrogen atom

4. C.  Neutral, with the number of protons equaling the number of electrons

lizards have adapted to life in the desert. some desert lizards have toes with spiny scales to them run across the sand without sinking. some use the sand to hide from predators, or to search for small animals that they prey upon.