在下列实验中，试管内容物变成蓝色的是（ ）
| 试管号 | 试管内容物 | 条件 | 检测 | |
| 1 | 2mL浆糊十2mL纯唾液 | 37℃ | 10min | 3滴碘液 |
| 2 | 2mL浆糊十2mL清水 | 37℃ | 10min | 3滴碘液 |
| 3 | 2mL浆糊十2mL稀释10倍的唾液 | 37℃ | 10min | 3滴碘液 |
| 4 | 2mL浆糊十2mL纯唾液 | 95℃ | 10min | 3滴碘液 |
| 5 | 2mL浆糊十2mL纯唾液+2滴浓HCl | 37℃ | 10min | 3滴碘液 |
D