Which is not a hypothesis stated in the text for why the Cambrian explosion occurred? A) The different chemistry in the ocean made it easier for animals to secrete hard shells

B) Super volcano exploded changing the environment and causing change in the animals

C) Oxygen levels reached a level that allowed animals to be more efficient at using aerobic metabolism

D) The emergence of predatory animals that could move around and eat other animals favored animals that could move or protect themselves

either a donut or a sphere or a pancake or a flat sphere. it depends on where the vertical line is.

if the line goes through the center of the circle and is perpendicular to a diameter containing the center, then you get a flat circle.

if the line and the diameter of a the circle meet in the center of the diameter and at an angle, you get a pancake.

if the line is on the circumference of the circle and is at right angles   to the circle you get a ring.

if the line contains the diameter, you get a sphere.

the the line is parallel to the diameter and touches the circumference, you get a donut.

what are the following?

i literally just read the book and studied it for months so i could you, but i need to know where these questions are coming from. they are too general.

21 balloons is the story of professor william sherman's travels.

in 1883, he set off from san francisco for a balloon ride over the pacific and was found a month later floating with 21 balloons in the atlantic ocean. this seemed an astounding feat and everyone wanted to know what had happened.    

professor sherman was loyal, however, and said he would tell his tale first to the western american explorers club in san francisco, of which he was a member. this built up suspense for several chapters before he began to tell of the wonders of his adventures and the amazing island of krakatoa, an island which had just been blown up by a volcano.  

the residents of krakatoa are all millionaires who live under a "gourmet government" of their own devising. we get to see all the incredible adventures that creative people with unlimited resources would create according to the author.