In the following question the 1st and the last part of the sentence/passage are numbered 1 and 6. The rest of the sentence/ passage is split into four parts and named P, Q, R and S. These four parts are not given in their proper order. Read the sentence/passage and find out which of the four combinations is correct

1. In summer tiny oysters are collected.

P. Then each oyster is taken out and a small hole is drilled in its shell.

Q. There they are kept for three years.

R. A tiny piece of sand is put inside the oyster.

S. They are placed in trays and planted in the sea.

6. Then the oysters are again left in the sea.