The longest-lived stars are expected to undergo fusion reactions for years. a thousand a million a billion a trillion thousands of trillions of

The correct answer for the blank is - A billion years.

The most common star that is considered to be longest lived is Red dwarf (which is primarily formed of hydrogen gas).

During the nuclear fusion of star, tremendous gravity forces the nuclei of atoms to fuse together, thereby liberating large amount of energy, preventing the star from imploding under its own gravity.

Thus, the longest lived stars are expected to undergo fusion reaction for a billion years.

The correct answer would be trillion of years. :

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.

the water is warmed up by the sun and then it evaporates into the atmosphere. the sunlight warms the water by its heat. water is then cooled down and condensation takes place. the water then finally returns back to the earth by the process of precipitation in the form of rain or ice.

explanation: