Final answer:
Ribosomes are crucial for producing proteins, which are macromolecules necessary for cellular repair and function; thus, option D is the correct answer.
Step-by-step explanation:
The organelle important for producing macromolecules for cellular repair is D. Ribosomes. Ribosomes are molecular machines found within all living cells that perform protein synthesis. Proteins are essential macromolecules required not only for cellular repair but also for various cellular functions.
Ribosomes read the genetic instructions carried by an mRNA (messenger RNA) strand to synthesize proteins from amino acids. These proteins can then assume structural, enzymatic, and regulatory roles within the cell. Ribosomes are found either floating freely within the cytoplasm or attached to the endoplasmic reticulum, forming what is known as the rough ER, which is involved in protein modification and transport to the Golgi apparatus for further processing.