The ________(防御) mechanisms of the body help fight off infections.
Some plants have special chemicals called ____ that help speed up chemical reactions in their cells.
enzyme
catalyst
gland
glucose
The new plant species was able to ____ the native ones for resources and space.
migrate
bind
outcompete
inherit
The plant is a type of ____(豆荚) which can fix nitrogen from the air into the soil.
The tall trees in the forest formed a thick ____ that blocked much of the sunlight from reaching the ground.
canopy
acorn
twig
trunk
Some tribes are ____(游牧的) and move from place to place in search of food and water.
The statue was so ________ that it required a crane to move it.
small
light
delicate
massive
The dog was trained to ________ the newspaper every morning.
Regular exercise and a healthy diet contribute to human ________.
strength
flexibility
endurance
longevity
The architects are working on ________ the blueprints for the new building.