What is the composition of an isotope of calcium (atomic number 20)?

The answer to your question is: last option.

20 protons

20 electrons

25 neutrons

Explanation:

Data

Calcium, atomic number 20

Atomic number indicates the number of protons in an element, so, if Calcium's atomic number is 20, it means that it has 20 protons.

In a neutral element, the number of protons = number of electrons, then

Calcium has 20 electrons.

Only the number of neutrons could change.

According to the previous description, the last option is correct. ( also put the options too)

it is

a

asked for and recieved from the united states

the berlin blockade was an international crisis that arose from an attempt by the soviet union, in 1948–49, to force the western allied powers (the united states, the united kingdom, and france) to abandon their post-world war ii jurisdictions in west berlin. in march 1948 the allied powers decided to unite their different occupation zones of germany into a single economic unit. in protest, the soviet representative withdrew from the allied control council. coincident with the introduction of a new deutsche mark in west berlin (as throughout west germany), which the soviets regarded as a violation of agreements with the allies, the soviet occupation forces in eastern germany began a blockade of all rail, road, and water communications between berlin and the west. on june 24 the soviets announced that the four-power administration of berlin had ceased and that the allies no longer had any rights there.