Which of the following statements is an inference?

a. she counts the robins in her yard once a week for two years.

b. she thinks some robins must migrate in the winter.

c. student notices that there are fewer robins in her yard during the winter.

d. she finds that there are about half as many robins in her yard in the winter as in the summer.

Cryolite, na3alf6(s), an ore used in the production of aluminum, can be synthesized using aluminum oxide. start this question by first balance the chemical equation.1.) balance the equation: - alo3(s)+naoh(l)+hf(> na3alf6+h2o(g). 2.) if 17.5 kilograms of al2o3(s), 51.4 kilograms of naoh(l), and 51.4 kilograms of hf(g) react completely, how many kilograms of cryolite will be produced? 3.)which reactants will be in excess, (al2o3, naoh, or hf) 4.)what is the total mass of the excess reactants left over after the reaction is complete in kg?