To solve this problem, we need to determine which type of RNA is most abundant in an animal cell. Let's analyze each type of RNA:$\newline \bullet$tRNA (transfer RNA):$\newline$ - tRNA is responsible for bringing amino acids to the ribosome during protein synthesis.$\newline$ - It is essential for translation but is not the most abundant RNA.$\newline \bullet$mRNA (messenger RNA):$\newline$ - mRNA carries the genetic information from DNA to the ribosome, where it serves as a template for protein synthesis.$\newline$ - mRNA is less abundant compared to rRNA because it is synthesized and degraded rapidly.$\newline \bullet$miRNA (microRNA):$\newline$ - miRNA is involved in the regulation of gene expression by binding to complementary sequences on target mRNAs.$\newline$ - It is present in small amounts compared to other types of RNA.$\newline \bullet$rRNA (ribosomal RNA):$\newline$ - rRNA is a structural component of ribosomes, which are the sites of protein synthesis.$\newline$ - rRNA is the most abundant type of RNA in the cell because ribosomes are present in large numbers to meet the cell's protein synthesis needs.$\newline$Therefore, the most abundant RNA in an animal cell is rRNA.$\newline$This corresponds to Option 4.