"Fifth sentence: Selecciona la opción de descarga en PDF."

I need to be careful with words like "botánica" which might have specific scientific synonyms. Maybe alternatives like botánica or similar. Also, the word "estudios" can be replaced with investigación.

Starting with the first sentence: "Tomás Emilio Díaz González es un experto en botánica con amplia experiencia en la enseñanza y la investigación." Proper names are already there, so I'll leave them. "es" can be replaced with "es|es|es" since it's a pronoun. "experto" has synonyms like "especialista|aficionado|maestro." Wait, "aficionado" might not fit here if the original is "experto." Maybe "especialista|llevado|ducho." Need to check for synonyms that fit the context. "en" can be "en|con|respecto a." Continue this process for each word, checking for three suitable synonyms.

The original instruction says "Proper nouns stay". The title is in quotes, so it's a noun phrase. However, "Curso de Botánica" is not a proper noun but a course title. But in Spanish, sometimes titles are treated as proper nouns. However, the user might consider the course title as a proper noun. If that's the case, the entire "Curso de Botánica" should stay. But maybe the user wants to modify the words within the title. I'm a bit confused here. Let me proceed step by step.

"Sistemática y taxonomía: clasificación y nomenclatura de las plantas" – "sistemática" can be sistemática? Wait, taxonomía is already mentioned, so maybe sistema but need three. Maybe taxonomía but I need to ensure accuracy.

Starting with the first word "El". As an article, maybe it can be swapped with "La", "Un", "Ese". Next word is "Curso", which can be "Programa", "Clase", "Lección". Then "de" might stay as is or be replaced by "para", "con", "en". But "de" in the context of a title might be part of the proper noun. Hmm. Since the user says "proper nouns stay", but the title itself is a common noun phrase. Maybe the user wants to keep the entire title as is. Alternatively, break it down. This is ambiguous. The instruction says "swap each word with 3 alternatives as spintax w2. Proper nouns stay." So every word except proper nouns. So the name "Tomás Emilio Díaz González" is a proper noun and should remain. But the rest of the words are common nouns and can be replaced. So "Curso de Botánica" is not a proper noun, so each word can be swapped.

Then the section on "Fotosíntesis y respiración: procesos fundamentales para la vida de las plantas". "Fotosíntesis" might be fotosíntesis but I need better alternatives. Maybe fotosíntesis. Let me verify those.