Question

A major purpose of this series on Environmental Chemistry, therefore, is to present a reasonably uniform view of various aspects of the chemistry of the environment


Como passar esta frase para o present perfect?

Basta substituir is to present por has present ?

Answer 1

Resposta:

A major purpose of this series on Environmental Chemistry, therefore, HAS BEEN  to present a reasonably uniform view of various aspects of the chemistry of the environment

Explicação:

Basta mudar o IS que está no presente  para o HAS BEEN que esta no present perfect