Why do sound waves move faster through the ground than through the air?
a. particles of matter are packed more loosely in the ground than in the air.
b. particles of matter are packed more tightly in the ground than in the air.
c. air doesn’t contain any particles of matter to transmit sound waves.
d. the elevation of the ground is lower than the elevation of the air space.

The answer is option A.

Explanation:  Particles of matter are packed more loosely in the ground than in the air. This is true because it doesn't have thig like buildings and people stopping the sound waves.

the answer is to check all of them! they all apply well at least i think so!

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.