Answer i will give which of the following are basic challenges of life for every organism? a. obtaining and using energy b. reproducing c. maintaining structure d. all of the above

D; You could make some argument for A only but for this the best answer would be D

The traits that are challenges of life for all organism is : 

A. Reproducing,

Both male and female seek the partners that potentially provide the best genetics

D. Maintaining structure

That's why we strive to provide necessary nutrition for our body such as protein and calcium

F. Obtaining energy

To do our day to day activities we need calorie consumption

hope this helps

not clear

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.