As the Polypeptide Is Elongating in Translation,what Is the Ribosome

As the polypeptide is elongating in translation,what is the ribosome doing?

A) removing incorrectly added amino acids.
B) moving along the mRNA transcript bonding amino acids to each other.
C) travelling back and forth between the nucleus and the growing polypeptide with information on which amino acids to add.
D) removing the non-coding introns.
E) doing more than one of these functions.