Calculate the mass in grams of each sample. Express your answer using two significant figures.
A.4.88x10^20 H2O2 molecules
B. 2.1x10^22 SO2 molecules
C. 5.3x10^25 O3 molecules
D. 9.12x10^19 CH4 molecules

How did the completion of the transcontinental railroad change the lives of american citizens? a-it increased the wealth of all americans and enabled them to travel more.b-it made cross-country travel too expensive for ordinary americans.c-it decreased the safety of americans who moved to settle the plains.d-it shortened travel time between the east and west for all americans.

Brainliesttt asap!me : describe the responses to terrorism in the united states.

U.s. history 1.documentary analysis what steps did taylor’s family take to prepare her freedom