词汇	天灾降临
释义	天灾降临 a natural calamity happens to/befalls sb天灾
随便看	stratified randomized design stratified random sampiing stratified random sample stratified random sampling Stratified random sampling for percentages stratified random sampling method stratified random samplingmodel stratified random sampling surveys stratified randon sampling stratified rate stratified ratio estimate stratified ratio or rgeression estimates stratified reconstruction stratified regression estimate stratified regular space stratified relief stratified reservoir stratified rock stratified rock mass stratified rock masses stratified rocks stratified rock sample stratified rock slope stratified roof stratified sample