What is the average age of menarche (first menstruation)?

Many state and local authorities are making laws regarding recreation on lakes, rivers, and oceans to reduce water pollution. why would lawmakers need to consult with scientists before making these laws? a) to make scientists feel important b) so that the laws reduce pollution by a sufficient amount c) so that parks and lakefront facilities will still make large profits d) so that the public will believe that the laws are important to follow

Which of these statements best describes the st. lawrence seaway? the st. lawrence seaway connects the st. lawrence river with the arctic ocean. the st. lawrence seaway provides an important trading route between the u.s. and mexico. the st. lawrence seaway provides an important trading route for the u.s, but has little value for canada. the st. lawrence seaway connects the great lakes, the st. lawrence river, and the atlantic ocean.

When analyzing tree rings, what do scientists assume a thin ring indicates?