已知二维连续型随机向量<img src="/lqwvjeImg/50/5089307c1c699815fb413ae3caf51cc1.png"style="width:321px;height:54px;">则常数<img src="/lqwvjeImg/06/06c48ee3d9b42439abd40dc3d5987639.png"style="width:25px;height:15px;">( )。<br>·<img src="/lqwvjeImg/34/348fcb9fb696036938ba39a6f105b13f.png"style="width:15px;height:41px;">;<br>·<img src="/lqwvjeImg/0f/0ff2f9a5ed8878beaf44ff7404a5262a.png"style="width:21px;height:41px;">;<br>·<img src="/lqwvjeImg/6b/6b6a7b56331f7e6f3088c19c3fa364d7.png"style="width:15px;height:41px;">;<br>·<img src="/lqwvjeImg/5f/5f040535f225ddef8c91d3ff01a0393b.png"style="width:16px;height:41px;">.