2007年(平成19年)センター試験英語第5問B「ヴィジュアル会話文」問2

次の会話文について、下の問に答えよ。

　Carol and Tomo are in the school cafeteria. They've just finished lunch and have a little time before their next class begins.

Carol : I've just learned a new game. Would you like to try it?

Tomo : Sure.

Carol : I have a clean sheet of paper, so all you need is a pencil.

　She marks three dots on the paper with her pencil.

Carol : The game begins with these dots. Actually, you can start with any number of dots. But, at first, it's best to start with three or four.

　She adds another dot on the paper.

Tomo : Where on the paper do we mark the dots?

Carol : You can place them anywhere you like. Now, join any two dots with a line. Players toke turns drawing a line.

　She joins two dots that are next to each other with a curved line.

Tomo : Don't you have to draw a straight line?

Carol : No. Any kind of line will do. In fact, you can even make a loop starting and ending at the same dot. But you can't draw a line that cross itself, or any other line.

Tomo : O.K. And?

Carol : When you've drawn a line, put a new dot somewhere on it. Each dot may have only three lines connected to it. So, since a new dot places on a line already has two lines connected to it, it can only have one more.

Tomo : I see. Are there any other rules?

Carol : No. That's it. You continue playing until you can't draw another line.

Tomo : And the player who draws the last line is the winner?

Carol : Exactly. Now that you understand the rules, let's play!

問2
次の(　　)に入れるのに最も適当なものを、下の1〜4のうちから1つ選べ。

A player loses in this game when it is his or her turn and (　　).

1. all the dots are connected to each other
2. no line can be drawn
3. the dots are all surrounded by lines
4. one of the dots is surrounded by a line