A jeweler is setting eight gemstones-gamete. jade, malachite, opal. ruby, sapphire, turquoise, and zircon-around a circular bracelet. There are eight adjacent positions, numbered consecutively 1 through 8 around the bracelet, in which to set the stones, with position 8 adjacent to position 1. The setting of the stones must conform to the following conditions:
The ruby is adjacent to the zircon.
The garnet is adjacent to the zircon.
The jade is adjacent to the opal.
The jade is not adjacent to the malachite.
If the turquoise is set in position 2, the opal is set in position 3; otherwise. the opal is set in position 2.
Step 1: Understand the condition.
We are given that the turquoise is set in position 8. We need to analyze each option and check which one must be true based on this condition.
Step 2: Analyze the options.
(A) The garnet is set in position 5.
We cannot deduce that the garnet must be in position 5 simply because the turquoise is in position 8. Therefore, this option is not guaranteed.
(B) The jade is set in position 1.
No immediate constraint or rule ties the jade to position 1 when turquoise is in position 8. This option is not required.
(C) The jade is set in position 3.
Like option (B), there is no direct rule forcing the jade to position 3 based on the turquoise's placement. Therefore, this is not a required conclusion.
(D) The malachite is set in position 1.
Similar to the previous options, there is no rule here that dictates the malachite must be in position 1. So this option is also not guaranteed.
(E) The sapphire is set in position 1.
Given the available options and constraints in the problem, we find that the sapphire must be in position 1. This is a consistent result that arises from the turquoise being in position 8.
Step 3: Final Answer
\[ \boxed{\text{The sapphire is set in position 1.}} \]

Two players \( A \) and \( B \) are playing a game. Player \( A \) has two available actions \( a_1 \) and \( a_2 \). Player \( B \) has two available actions \( b_1 \) and \( b_2 \). The payoff matrix arising from their actions is presented below:

Let \( p \) be the probability that player \( A \) plays action \( a_1 \) in the mixed strategy Nash equilibrium of the game.
Then the value of p is (round off to one decimal place).
Three friends, P, Q, and R, are solving a puzzle with statements:
(i) If P is a knight, Q is a knave.
(ii) If Q is a knight, R is a spy.
(iii) If R is a knight, P is a knave. Knights always tell the truth, knaves always lie, and spies sometimes tell the truth. If each friend is either a knight, knave, or spy, who is the knight?