The pitch of a sound is most closely related to the a. frequency of vibrations. b. distance from the sound source. c. medium through which the sound travels. d. intensity of the sound.

"frequency of vibrations"

Explanation:

The pitch of a sound is defined as the quality that is responsible to judge any sound. The pitch of a sound is most closely related to the frequency of vibrations. Pitch is directly related to the frequency of the sound wave.

If the pitch is high, it will have high frequency and if the pitch is low, it will have low frequency. But the loudness of sound depends on the amplitude of the sound wave. The energy of the wave defines the loudness of the wave.

Hence, the correct option is (a) "frequency of vibrations".

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.