**Core Concept**
Paramyxoviruses are a family of enveloped viruses that possess a single-stranded RNA genome of negative polarity. They are characterized by their unique replication strategy and mode of entry into host cells.

**Why the Correct Answer is Right**
Paramyxoviruses contain a single-stranded RNA genome of negative polarity, meaning that the RNA is complementary to the mRNA transcript. This is a characteristic feature of negative-sense RNA viruses. Furthermore, the envelope of paramyxoviruses is derived from the host cell's plasma membrane, which is a common feature among enveloped viruses.

In terms of replication, paramyxoviruses replicate in the cytoplasm of host cells, which is a key feature of these viruses. This is in contrast to DNA viruses, which typically replicate in the nucleus. Finally, paramyxoviruses enter the body primarily through the respiratory route, which is the typical mode of entry for these viruses.

**Why Each Wrong Option is Incorrect**
* **Option C:** While paramyxoviruses do replicate in the cytoplasm, this is not unique to them, and other viruses also replicate in this compartment. However, the question asks for a characteristic that is true of all paramyxoviruses, and replication in the cytoplasm is not exclusive to this family.
* No further explanations are needed for **Option A** as it is not a possible choice given the correct answer is B.

**Clinical Pearl / High-Yield Fact**
Paramyxoviruses include several important human pathogens, such as measles, mumps, and respiratory syncytial virus (RSV). These viruses are responsible for significant morbidity and mortality worldwide, and understanding their characteristics is crucial for developing effective diagnostic and therapeutic strategies.

**✓ Correct Answer: B. abcd. All paramyxoviruses contain a single-stranded RNA genome of negative polarity, their envelope is derived from the host cell's plasma membrane, they have a cytoplasmic site of replication, and they enter the body primarily through the respiratory route.**