Theboysliketolistentomusicwhentheydo______(they)homework.

Theofficebuilding_____theclassrooms

薇甘菊为入侵我国的植物，田野菟丝子茎缠绕在薇甘菊植株上，茎上即可形成吸器吸收薇甘菊植株中的营养物质。

JackisateacherofEnglish.Heisnotyoung，butheisnotold.Hehasaroundfaceandblackhair.Heistall.Therearefiftystudentsinhisclass.Theyalllikehim.Nowit'sintheafternoon.Look，somestudentsareworkingintheclassroom.Jackisthere，too.HeishelpingthemtostudyEnglish.Heisagoodteacher，andheisagoodfriendofthemall.

()1.WhatdoesJackdo?

A.Heisaworker.

B.Heisateacher.

C.Heisadoctor.

D.He'sanurse.

()2.Whatcolourishishair?

A.It'sblack.

B.Hisheiriswhite.

C.Itisbrown.

D.Hehasyellowhair.

()3.Howmanystudentsarethereinhisclass?

A.Therearefifteenstudentsinhisclass.

B.There'sfifty.

C.Hehasfifty.

D.There'refiftyinit.

()4.Jackisagoodteacher，isn'the?

A.Yes，heisn't.

B.No，heis.

C.Yes，he's.

D.Yes，heis.

()5.Whatarethestudentsdoingintheclassroom?

A.Theyarewalkingthere.

B.Theyaredoingtheirlessons.

C.Theyarehelpingtheirteacher.

防御素是一类具有抗菌活性的蛋白质，广泛存在于动物体中。有关说法错误的是