增加选择声调提示图

src/views/exercise_questions/preview/ChooseTonePreview.vue

@@ -102,7 +102,16 @@
       </li>
     </div>
     <div class="answer-tips-box">
-      <img v-if="show_tips" class="answer-tips" src="../../../assets/select-tone-tips.png" />
+      <img
+        v-if="show_tips && data.property.answer_mode === 'label'"
+        class="answer-tips"
+        src="../../../assets/select-tone-tips.png"
+      />
+      <img
+        v-if="show_tips && data.property.answer_mode === 'select'"
+        class="answer-tips"
+        src="../../../assets/select-tone-tips-2.png"
+      />
       <span :class="['tips-btn', show_tips ? 'tips-btn-active' : '']" @click="show_tips = !show_tips">
         <img src="../../../assets/tips-icon.png" />
       </span>