A:In fact
B:Luckily
C:Naturally
D:Unfortunately
“十月怀胎,一朝分娩”,胎儿和母亲血脉相连.胚胎在母体内发育的场所是____,胎儿通过____、脐带从母体获得营养物质和氧.
What are the ________ doing? ( )