单选题设总体X服从均匀分布U（1，θ），<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251114/23827441_0.png">，则θ的矩估计为（　　）。<br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251114/23827441_0_1.png">