Police Officer 1: So, how on earth did they manage to get in? There's no sign of a forced entry.
Police Officer 2: Well, I suppose they could have got in through a window up on the fourth floor.
Police Officer 1: But no one would have dared climb up the outside of the building. Anybody trying to do that would have been seen from the street below. You don't think they would have been able to jump from the block across the road, do you?
Police Officer 2: No, it's much too far. Of course, there's always the fire escape around the back of the building. They could have climbed up there reasonably easily, and after that they might have been lowered by rope from the roof. If that was the case, people living in the block of flats behind the museum might have seen something, so we need to talk to them.
Police Officer 1: Right, but we needn't interview everyone in the block, just the people who have windows facing the museum. I'll arrange that.
Police Officer 2: If it wasn't a window, the only other possibility is that they went in through the front door. Perhaps they forced the lock, but the door didn't appear to be damaged at all.
Police Officer 1: And the entry code is supposed to be known only by the security guard.
Police Officer 2: So someone else must have opened the door from the inside.
Police Officer 1: Only the security guard was allowed to stay in the museum after it closed. Do you think they somehow persuaded him to let them in? Maybe they just knocked on the front door and he opened it.
Police Officer 2: He surely wouldn't have done something as stupid as that. Do you think he might have been expecting them and that he was part of the gang?
Police Officer 1: But then why would they have attacked him?
Police Officer 2: I don't know, but we'd better find out all we can about that guard as soon as possible. Now, who was it that raised the alarm?
Police Officer 1: It was the head cleaner, who went into the building early this morning. He must have to know the entry code, too.
Police Officer 2: Yes, maybe. He says the front door was unlocked when he got here. But he claims he didn't see anything else unusual until he got to the fourth floor. But of course, he might be lying.
Police Officer 1: Yes, he must know that he ought to have called the police as soon as he found the door open. I wonder why he didn't. I think we should talk to him again. I suppose he could be hiding some information from us, and he might be prepared to tell us more if we put a bit of pressure on him.
Police Officer 2: The other puzzling thing is how they took the paintings away. Apparently, they're very big, so the robbers must have had to bring a van around to the front of the building.
Police Officer 1: The driver must have been waiting nearby and drove up when they'd got the paintings. They could have loaded the paintings up very quickly, and might have driven straight to a port or airport. Anyway, the forensic team should have finished examining the building by now. Once they've done that, I think we should go and look around for ourselves …
Answers are shown above — check your thinking against them.
But of course, he might be lying. (= present: it's possible he's lying)
They could have got in through a window. (= past: it's possible they got in)
Someone else must have opened the door. (active — certain past deduction)
It must have been opened from the inside. (passive)
I daren't criticise him. (modal + bare infinitive) / She dared me to jump. (ordinary verb + to-infinitive)
A good car needn't cost a lot. (modal) / We need to talk. (ordinary verb)
B: Yes, I think it could by morning.
B: They think it may by a gas leak.
B: It certainly used to be, but it may since then — I haven't been there for years.
B: He must in the garden.
B: You might it easier if you'd been wearing gloves.
B: Yes, but I can't see her. I suppose she might for us inside.
B: Well, if the salary was higher I might but it was even less than I'm earning now.
B: Well, she could about someone else, I suppose.