This is a classic example of a scope shift. The evidence (the first sentence) compares the Silver Bullet to other "high-speed trains." The conclusion compares it to all trains. Just because a train has few delays relative to other high-speed trains doesn't mean it has few delays (or is "efficient") compared to ALL trains. Look for a choice that points out the scope shift.

Choice (C) does that. If high-speed trains are often delayed, then argument is weakened. It exposes the flaw in the argument, which is along the lines of "Alex is the smartest ‘D' student in the class." (C) is correct.