a. I have never seen

b.   1) left        2) started

c. wouldn't have stopped

d.   1) once stayed      2) liked

e. just arrived

f.   1) was       2) were    3) preferred

g. would be

h. was

Bonjour

present, past, present perfect, past perfect, conditionnal

a- "I have never seen such beautifully preserved animals" he said. (present perfect)

b- Billy left the station and started looking for a pub. (past)

c- "I wouldn't have stopped if I hadn't seen the sign", he said. (conditionnel passé)

d- Billy had stayed in a pub before and once liked it. (past perfect + past)

e- I just arrived from London", Billy explained to the landlady. (past)

f- It is well-known that landladies are rarely generous and Billy therefore preferred staying in a pub. (present + past)

g- Billy thought that if he stayed in the B&B, it would be more comfortable and cheaper. (conditionnel)

h- All this time, the dog had been (was) as quiet and motionless as  the parrot. (past perfect  /ou/  past) .

bonne soirée ☺☺☺