Why is Mendeleev's suggestions best accepted in the construction of the periodic table

Look at the reaction below: ca(hco3)2 --> caco3 + co2 + h2o first, balance the reaction. once balanced, use dimensional analysis or another method to find out how many moles of carbon dioxide will be produced if we start with 16.5 moles of calcium bicarbonate (calcium hydrogen carbonate). = mol of co2 number needs to be reported to three significant figures.

Which traits do human embryos have that link them to a common ancestor with fish and reptiles? a. scales and tail b. gill slits and scales c. tail and gill slits d. hair and tail

Idon’t know how to solve this question