1 : Charles Goodyear once accidentally
P : and found that the resulting rubber
Q : dropped a mixture of natural rubber
R : was harder, stronger, more elastic
S : and sulphur over a hot stove
6 : and non-sticky
The Proper sequence should be:
A. PSQR
B. QSPR
C. RSQP
D. SQPR
Answer: Option B

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