A porpoise sends out an ultrasonic burst and hears the echo off his favorite food in 0.13 seconds. How far away is the food source? Assume that sound travels at 1,530 m/sec in water

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.

the answer is true. hope it .

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)

the answer is b because, investigating whether another species of moth also drinks tears might be interesting, but it would not directly explain why this species of moth does.

to explain why this species of moth drinks tears, the scientist could ask: "what nutrients that moths need are in elephant tears? "

the scientist could experiment with moth repellent or oter ways to keep the moths away, but that would not answer his original question.