Which of the following statements about protostars is true?
a) protostars do not always become stars.
b) protostars never become stars.
c)scientists do not yet know if protostars ever become stars.
d) protostars always become stars.

Which of the following represents an upside-down image? o a. +doo b. -doo c. +mo d.-m

In which of the following would the particles move most rapidly? a. ice at -20 °c b. water at 20 °c c. steam at 110 °c d. boiling water e. ice at 0 °c

Global warming will produce rising sea levels partly due to melting ice caps but also due to the expansion of water as average ocean temperatures rise. to get some idea of the size of this effect, calculate the change in length of a column of water 1.00 km high for a temperature increase of 1.00ºc. note that this calculation is only approximate because ocean warming is not uniform with depth. (answer in ×10^{-3} −3 m)