The thermostat in a refrigerator filled with cans of soft drinks malfunctions and the temperature of the refrigerator drops below 0 °c. The contents of the cans of diet soft drinks freeze, rupturing many of the cans and causing an awful mess. However, none of the cans containing regular, non-diet soft drinks rupture. Select the statement or statements below that best describe this behavior.

If (a, b) is the solution to the system of equations shown above, and a and b are integers, then what is the value of a+b?

Assessment includes a. interviews, recorded conversations, videos, frequency counts, and time samples. b. formal standardized tests and developmental screening tools. c. various types of documented observations, documentation of child work, checklists, rating scales, and standardized tests. d. anecdotal notes, narratives or daily records, daily health checks, and teacher observation checklists.

Summarize the work of famous environmental scientists of the past.