What Does It Mean When It Is Said in Solr

Multiple Choice

What does it mean when it is said in Solr indexing that the index is "eventually consistent"?

A) The index will only be consistent after a server restart.
B) The index will become consistent when there are no more transactions to index.
C) The index becomes consistent once a day when the index job runs.
D) The index can only be consistent when the Lucene index job eventually runs.