It has been theorized that all of the modern continents on earth were once part of a single continent. what scientific evidence is used to support this theory? a. the coastlines of some modern continents appear to have once fit together. b. fossils of similar lifeforms have been found on different continents. c. some of the continents that exist today have similar types of rocks.

(its a multiple choice answer)

Evidence is not used to support a theory. A hypothesis is proposed to explain evidence, and then tested to produce a theory.

Choices A, B, and C have all been observed. The theory of Pangea/continental drift was formulated to explain them.

d. learned preferences i believe is your answer

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.