題目下列那個分子不是體內合成胸苷單磷酸(thymidine monophosphate, TMP)的重要前驅物?A.天門冬胺酸(aspartate)B.磷酸核糖焦磷酸(phosphoribosyl pyrophosphate, PRPP)C.葉酸(folate)D.甘胺酸(glycine)官方答案D