makefile编译多线程时发生错误，如何解决？

Question

代码段

makefile段

运行结果及报错内容

cc pthread_more.o -o pthread_more
/usr/bin/ld: pthread_more.o: in function main': /home/zhang/Linux_01/pthread/pthread_more.c:22: undefined reference to pthread_create'
collect2: error: ld returned 1 exit status
make: *** [<内置>：pthread_more] 错误 1

makefile要怎么修改