Which of the following explains why sub-surface mining is more dangerous than surface mining? a. Sub-surface miners deal with loud noises in addition to surface mining hazards such as toxic air conditions, sinkholes, and machine injuries.
b. Sub-surface miners deal with toxic air conditions in addition to surface mining hazards such as sinkholes, machine injuries, and loud noises.
c. Sub-surface miners deal with hazardous chemicals in addition to surface mining hazards such as toxic air conditions, sinkholes, and loud noises.
d. Sub-surface miners deal with machine injuries in addition to surface mining hazards such as toxic air conditions, sinkholes, and loud noises.

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.  

they are called fossil fuels

the term hydride is commonly named after binary compounds that hydrogen forms with other elements of the periodic table. hydride compounds in general form with almost any element, except a few noble gases. the trends and properties vary according to the type of intermolecular force that bonds the elements together, the temperature, its molecular masses, and other components. hydrides are classified into three major groups, depending on what elements the hydrogen bonds to. the three major groups are covalent, ionic, and metallic hydrides. formally, hydride is known as the negative ion of a hydrogen, h-, also called a hydride ion. because of this negative charge, hydrides have reducing, or basic properties. its special characteristics will be further discussed.

explanation: