Questions

An electric fuse is based on the heating effect of the current.

While plant cells have chloroplasts to photosynthesize, they also require ATP for cellular functions, and do use oxygen to break down some of the sugar they produce in order to generate that ATP. Cellular respiration takes place in the mitochondria. They need mitochondria for this reason.
Hence with this logic, we can say that Plants cells have mitochondria.

The statements true about viruses are :

1. The capsid enters the host cell if the virus is enveloped.

2. Enveloped viruses bud from the host cell. 

3. HIV contains reverse transcriptase.

4. A retrovirus contains RNA.

No improvement required. Sentence is idiomatically correct.

Right after that, the mRNA enters the cytoplasm through nuclear pores. There, it could be translated into proteins by ribosomes. This process is called translation.

Translation occurs in the cytoplasm whereas transcription occurs in the nucleus.