定语从句只能用that的情况:
1.先行词是不定代词:
all,few,little,much,something,nothing,anything等.
2.先行词被序数词或形容词最高级所修饰.
3.先行词被all,any,every,each,few,little,no,some,等修饰.
4.先行词被 the only,the very,the same,the last 修饰时.
5.先行词既有人又有物时.
你这里属于第二种情况.the first 是序数词.
定语从句只能用that的情况:
1.先行词是不定代词:
all,few,little,much,something,nothing,anything等.
2.先行词被序数词或形容词最高级所修饰.
3.先行词被all,any,every,each,few,little,no,some,等修饰.
4.先行词被 the only,the very,the same,the last 修饰时.
5.先行词既有人又有物时.
你这里属于第二种情况.the first 是序数词.