निम्नलिखित में से कौन सा प्रतिचित्रण d: ℝ × ℝ → ℝ, ℝ पर एक मान्य दूरीक (metric) को परिभाषित करता है?

Let E = [0, 1] and f: ℝ → ℝ be defined as f(x) = d(x, E), where d is the standard metric on ℝ defined as d(x, y) = |x - y|. Then which of the following options is true?

Let A ⊆ ℝ be the closed interval [1, 3] equipped with the standard topology. Which of the following statements is correct?