电话是在1876年发明的。翻译
Manyothernewtechniquesarenowavailablethatenablemoreresearch___(do)inthetesttubetoseeifchemicalsproduceharmfulbiologicaleffects.
在双缝干涉实验中,屏幕上P处是暗条纹,则两束相干光在P处的光程差可能是()
Ifyouhadbeeninbetterhealth,we___(allow)youtojointheminthework.
Iwouldverymuch______tovisitsomeoftheplacesthatIhavebeenreadingabout.