There is a proverb in the microcosmic world of snowflakes. The riddle is: &”;Bluestone is on the terrace, and flowers bloom on the stone, but all flowers have leaves. Guess on the leafless one.&”; This riddle is a natural phenomenon in the winter.

12. For example. Comparing the shape of snowflake to hexagon, hexagon and spider web vividly describes the beautiful and changeable features of snowflake, which enhances its literary characteristics and is more readable. 13. It refers to &”;water vapor in the distance&”;. 14, can not be deleted, &”;often&”; means that in most cases, if removed, the dendritic snow crystals that become snowflakes are generated in an environment of about 15 degrees and containing a lot of water vapor, which is not in line with the actual situation; It embodies the accuracy of explanatory language. 15. ① Snowflakes are formed by the continuous condensation of water vapor in the clouds on ice crystals, and this ice crystal itself has a hexagonal structure. (2) concentration of surrounding water vapor (3) surrounding temperature (4) existence of other gases in the air (16).