You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Imperial_College_London

Context:
The 2008 Research Assessment Exercise returned 26% of the 1225 staff submitted as being world-leading (4*) and a further 47% as being internationally excellent (3*). The 2008 Research Assessment Exercise also showed five subjects – Pure Mathematics, Epidemiology and Public Health, Chemical Engineering, Civil Engineering, and Mechanical, Aeronautical and Manufacturing Engineering – were assessed to be the best[clarification needed] in terms of the proportion of internationally recognised research quality.

Question:
How many subjects were judged to be the best in terms of internationally recognised research quality?

five