A、<p><span lang="EN-US" style="font-size: 10.5pt; font-family: 宋体;">2 </span><span style="font-size: 10.5pt; font-family: 宋体;">′，<span lang="EN-US">3</span>′一磷酸二酯键</span></p>
B、<p><span lang="EN-US" style="font-size: 10.5pt; font-family: 宋体;">5</span><span style="font-size: 10.5pt; font-family: 宋体;">′，<span lang="EN-US">3</span>′一磷酸二酯键</span></p>
C、<p><span lang="EN-US" style="font-size: 10.5pt; font-family: 宋体;">3</span><span style="font-size: 10.5pt; font-family: 宋体;">′，<span lang="EN-US">5</span>′一磷酸二酯键</span></p>
D、<p><span lang="EN-US" style="font-size: 10.5pt; font-family: 宋体;">1 </span><span style="font-size: 10.5pt; font-family: 宋体;">′，<span lang="EN-US">3</span>′一磷酸二酯键</span></p>
E、<p><span lang="EN-US" style="font-size: 10.5pt; font-family: 宋体;">1</span><span style="font-size: 10.5pt; font-family: 宋体;">′，<span lang="EN-US">5</span>′一磷酸二酯键</span></p>