To check spelling errors in a document, the Word application uses the to determine appropriate spelling.

other text in the document
user-defined words
built-in dictionary
Internet

built-in dictionary

Explanation:

Can you ever imagine making use of other text in the document for finding the meaning? They help but only when we are concerned about the intent, and it is a tough method. The word application makes use of the built-in dictionary in reality, and the use of other text in the document is now done through the new version, but to find the intent. And the internet is never used, as this software is required to work offline as well. And user-defined words are only a few, whereas the built-in dictionary covers all words. And hence built-in dictionary is the correct option here, and manuals also confirm this.

these  signals travel  down a part of the neuron called the axon, which is like a wire that carries the  signal  to othernerve  cells. on average a  nerve  cell sends a  signal  at about 50 meters per second, which is over 100  miles  an hour!