iOS应用内存使用量在Xcode中持续增长

我是iOS编程的新手,我刚刚构建了一个iPhone应用程序,可以向用户提问并返回答案.构建环境是OS X 10.9和 Xcode 5.0.2.每次启动iPhone模拟器时,Debug Navigator都会显示内存使用量为13.5mb,但即使在我返回主屏幕后它也会继续运行.一分钟后,内存使用量将稳定在17.5mb左右.这是正常的行为还是我需要添加一些内存管理代码？

#import "QuizViewController.h"

@interface QuizViewController ()

@property (nonatomic) int currentQuestionIndex;
@property (nonatomic,copy) NSArray *questions;
@property (nonatomic,copy) NSArray *answers;

@property (nonatomic,weak) IBOutlet UILabel *questionLable;
@property (nonatomic,weak) IBOutlet UILabel *answerLable;

@end

@implementation QuizViewController

- (instancetype) initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if(self){
        self.questions = @[@"From what is cognac made?",@"What is 8 + 8 ?",@"What is the capital of Minnesota?"];
        self.answers = @[@"Grapes",@"16",@"St.Paul"];
    }

    return self;
}

- (IBAction)showQuestion:(id)sender
{
    self.currentQuestionIndex++;
    if (self.currentQuestionIndex == [self.questions count]){
        self.currentQuestionIndex = 0;
    }
    NSString *question = self.questions[self.currentQuestionIndex];
    self.questionLable.text = question;
    self.answerLable.text = @"???";
}
- (IBAction)showAnswer:(id)sender
{
    NSString *answer = self.answers[self.currentQuestionIndex];
    self.answerLable.text = answer;
}

@end