I have an English exam tomorrow and I have a doubt on the passive voice...Do the following sound correct to you? The exercise asks to rephrase the sentences making them more formal, by using the impersonal passive forms below.
1. Police think the robbers entered through an open window.
a) It is thought that the robbers entered through an open window.
b) The robbers are thought to have entered through an open window.
2. Police say the murderer has disappeared.
a) It is said that the murderer has disappeared.
b) The murderer is said to have disappeared.
My doubt is on 1b) and 2b) because while the initial phrases have different verbal tenses (Simple Past and Present Perfect), the passive sentences both use Perfect Infinitive...but it's the only way it sounds good to me...