Hi, the crucial point in A level biology exams is that YOU NEED TO SPECIFICALLY ANSWER THE QUESTION - anything incorrect will NOT earn a mark, but neither will anything correct THAT IS IRRELEVANT or DOES NOT ADDRESS THE Q.
With the Q on viruses and Plasmodium, you would get your mark for (I quote), "that viruses need a host chromosome to insert their viral DNA into to code for viral proteins" because the fact that the virus NEEDS DNA is suggested by your answer saying "needs a host chromosome" AND that it needs this to "Synthesize proteins" you say to "code for proteins" - you have said enough for one mark.
However, your point about plasmodium part of Q says "plasmodium gains nutrition from the host," which does not explain "spends part of its life cycle in erythrocytes" in the Q. i.e. many parasites gain nutrition from the host e.g. tapeworm uses food ingested by the patient directly from the intestine, but THEY ARE NOT INTRACELLULAR - if you were to replace the word "erythrocyte" for "host" in your answer, you would have got that second mark.
I hope I have explained that YOU NEED TO ASSOCIATE YOUR ANSWER/POINT/IDEA/REASON directly to the actual Q asked to get a mark.
Look at some of my other posts to get further tips.
M (specialist biology tutor)