Step 1: Recall the genetic code.
Each amino acid is specified by one codon, and each codon consists of
\[
\boxed{3\ \text{nucleotide bases}.}
\]
Step 2: Calculate the number of amino acids.
Given,
\[
\text{Total nucleotide bases}=900.
\]
Therefore,
\[
\text{Number of codons}
=
\frac{900}{3}
=
300.
\]
Hence,
\[
\boxed{300}
\]
amino acids can be coded.
Therefore,
\[
\boxed{(B)}
\]
is the correct answer.