Kids at outdoor school look at pond water with teacher
Kids at outdoor school look at cup of pond water with teacher
Kids at outdoor school have group lesson by pond
Kids at outdoor school have group lesson by pond
Kids at outdoor school have group lesson by pond
Biochemist takes a sample of water from the local dirty pond
Biochemist takes a sample of water from the local dirty pond
Biochemist takes a sample of water from the local dirty pond close up
School teacher talking to kids before they get on school bus
School teacher taking register before kids get on school bus
School teacher takes register before kids get on school bus
Ecologist sample water from the river and get fishes dead to check effected case in laboratory, Biologist wear protect suit and mask collects sample of waste water from industrial, problem environment