What do you think of cats? Some people think very lovely. But not all people love cats. Compared with dogs, cats seem to be very lazy and unfriendly. Besides, cats are not known for acts of selflessness (无私). But maybe we're wrong about them. Don't believe it? Then meet Pippa, a very unusual cat.

    The black-and-white cat was left in a box outside a shop and taken by the British RSPCA to the Jansa family in Whitstable, Kent. They really loved her character (性格) and decided to adopt (收养) it，but they never guessed she'd become a lifesaver.

    Eight-year-old Mia Jansa had diabetes and had become good at testing her blood during the day, as well as having something to eat or drink to bring her blood sugar levels back. But the danger was at night. Mia could easily experience hypoglycemic (低血糖症的) situations when she was asleep, which could cause even death.

    Soon after she was adopted, Pippa went into Mia's bedroom in the middle of the night and woke her up. When the child tested her blood sugar levels, she found they were dangerously low. Ever since, Pippa always visits Mia at night. If she can't get her to wake up, she raises the alarm.

    “Pippa does this of her own accord,” says Mia's mother Laura. “We don't make a request for caring because we don't want to encourage wrong alarms. She gets plenty of hugs. It gives me peace of mind and I know someone else is keeping an eye on Mia.”

    Now the family is so happy that they've chosen to adopt it in the first place.

为探究生物制剂Q对阿霉素所导致的心肌细胞凋亡是否具有保护作用，研究者提出了以下实验设计思路：

第一步，进行实验分组：甲组加入培养液+心肌细胞+生理盐水、乙组加入培养液+心肌细胞+阿霉素、丙组加入培养液+心肌细胞+生物制剂Q+阿霉素．每组设置若干个重复样品，每组所加心肌细胞数相同．

第二步，各组样品在相同且适宜的条件下培养一段时间后，在显微镜下观察记录细胞数．

第三步，重复第二步若干次，统计计算____ （即实验因变量）．（填在第1小题）

请根据以上实验回答问题：

（1）该实验的因变量是：____．

（2）预测实验结果及结论：

①若____，则生物制剂Q对阿霉素致心肌细胞凋亡具保护作用．

②若____ ，则生物制剂Q对阿霉素致心肌细胞凋亡不具保护作用．

（3）与实验动物相比，采用离体心肌细胞为实验材料，可以避免实验动物的心脏活动受____ 调节的干扰．

（4）上述实验还可以增加一组，加入的物质是：____ ．