Ans. is 'b' i.e., D arm is for ribosomal attachment* tRNA or transfer RNA is so called because it transfers aminoacid from aminoacid pool to ribosome, which is the translation machinery* For coding 21 aminoacids we have 50 to 100 tRNAs, each coded by a unique gene* These tRNAs are clover leaf shaped* Every tRNA has four stable arms and 1 variable arm* The four stable arms are:i) Anticodon armii) Acceptor armiii) D armiv) TpsC armAnticodon arm* The triplet nucleotide that is complementary to the codon of mRNA. In anticodon, the first nucleotide of anticodon of tRNA is not specific or the nucleotide towards 5' end of anticodon is not specific. This is Wobble phenomenon. This explains how can 1 codon code for more than one aminoacid (Degeneracy of codon).* Acceptor arm is so called, because it is this arm which accepts the aminoacid. This arm has a triplet nucleotide "CCA" attached to the 3' end of tRNA. It is to the A of this CCA, to which aminoacid gets attached. This CCA triplet nucleotide is common to all the tRNAs, when all the other sequences are unique to a particular tRNA.TpsC arm* The arm through which the tRNA gets attached to ribosome,D arm* The arm through which aminoacyl tRNA synthetases get attached.# For every aminoacid, we have a specific aminoacyl tRNA synthetase# Once the enzymes - aminoacyl tRNA synthetases get activated, they go to the aminoacid pool. They pick up the specific aminoacid and activate the specific aminoacid using 2 high energy phosphates.# The activated aminoacids are carried by the respective enzymes and they go to the tRNA pool.# In the tRNA pool, they get attached to the tRNAs through D arm# Then they scan the anticodon arm, if the specific anticodon is found, the aminoacid is attached to acceptor arm.* Hence choice b, D arm is for ribosomal attachment is false. D arm is for aminoacyl tRNA synthetases attachment.