The gas used to fill party balloons contains only helium atoms. this makes helium a(n)

element

Explanation:

An element contains same kind of atoms. An element is a pure substance. A compound contains two or more atoms chemically combined together. A mixture contains different types of atoms which are not combined chemically.

A balloon contains a gas which is made up of only Helium atoms. The same kind of atoms make the gas. Thus, Helium is an element.

meteorologists would compare a new weather map with one 24 h old to see how fast a front is moving.

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.