Which statements represent convection? Select two options. Black asphalt gets very hot on a sunny day.
***The movement of air in a hot-air balloon makes it rise into the sky.
A dark sand beach can burn the soles of your feet.
A spoon gets warm from sitting in a soup pot.
A house has high heating bills because the heat ends up in the attic.
A house loses heat through an exterior wall.
*** means correct

the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.

the cell is the smallest structural and functional unit of living organisms, which can exist on its own. therefore, it is sometimes called the building block of life. some organisms, such as bacteria or yeast, are unicellular—consisting only of a single cell—while others, for instance, mammalians, are multicellular.