When carbon is added to iron in the proper proportions , the result is steel.

Someseaurchins海胆havevenomous(toxin)spines

The flower bud of a water lily 百合 opens at sunset since .its opening is triggered(commence) .by the decreased light.

Comets are still regarded with awe by some people.

Alllivingorganisms,regardlessoftheiruniqueidentity,havecertainbiological,chemical,andphysicalcharacteristicsincommon.