Answer:
I think its C a scientific journal article
Explanation:
Any kind of journal is considered a primary source because journals contain info that the original author wrote. Encyclopedias are considered teritary sources, but im not sure if that counts ...so id go with journals.

Here's the balanced equation for given Double displacement reaction ~

The products fored are : Lead Iodide ( PbI2 ) and Potassium Nitrate ( KNO3 )
Answer:
They could possibly make daily check ups to the research facility?
Answer:
H2O> NH3> CH4
Explanation:
According to valence shell electron pair repulsion theory (VSEPR), bond angles and repulsion of electron pairs depends on the nature of electron pairs on the central atom of the molecule. Lone pairs cause more repulsion (and distortion of bond angles) than bond pairs). Lone pair- lone pair repulsion is greater than lone pair bond pair repulsion.
Water contains two lone pairs on oxygen hence it experiences the greatest repulsion. Ammonia has only one lone pair on nitrogen hence there is lesser repulsion between lone pairs and bond pairs. Methane possess only bond pairs of electrons hence it has the least repulsion.