What is the missing first step of the following process: - The sound travels in waves, as sound does - The sound 'bounces' off of a nearby object - The sound wave returns to the bat - The bat hears the echoed sound - Folds in the bat's ear and adaptations in the bat's brain enable it to determine the size, shape, and position of the other object via the properties of the returned sound waves - Other animals use echolocation in generally similar ways -
Ans: Bats and other animals produce a high-pitched tone

What is the missing first step of the following process: - Babies become infants - Infants become children - Children learn skills - Children become teenagers - Teenagers undergo puberty - Teenagers become adults - Adults have children - Adults become elderly - Elderly humans die.
Ans: Humans are born as babies

What is the missing first step of the following process: - The plants and floor absorb the the sunlight - The absorbed sunlight is converted to heat - The heat cannot escape the glass - The heat is trapped in the greenhouse - The hot air rises - The colder air at the top is pushed to the bottom - The colder air is then warmed by the floor and the plants.
Ans: Sunlight passes through the glass into the greenhouse

What is the missing first step of the following process: - Chemicals from the acid rain kill plants and trees - The acid rainwater flows into rivers and streams - The chemicals kill fish - The chemicals kill animals that drink the water - Nitrogen builds up - Nitrogen destroys fish and shellfish populations.
Ans: Acid rain flows through soil