'RTC_DS1307' does not name a type

I have a problem with my code. The error says "'RTC_DS1307' does not name a type". Please, i realy need this for my college. thanks.
Here's the code:
#include "RTClib.h"
#include <SPI.h>
#include <SD.h>
#include "DHT.h"
#include <LiquidCrystal.h>

#define DHTPIN A1 // pino de leitura do DHT (sensor de temperatura)
#define DHTTYPE DHT11 // DHT 11
DHT dht(DHTPIN, DHTTYPE);
const int rs = 9, en = 10, d4 = 7, d5 = 6, d6 = 5, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
RTC_DS1307 rtc;
File file;

byte cs_pin = 10;
int start_time = 0;
int timeout = 0;

int pin_a0 = A5; //pino de leitura do sensor de gas
int nivel_sensor = 250;

void setup()
{

start_time = millis();
Serial.begin(9600); //Seta padrao de comunicacao

Serial.println("Starting SD card...");
if (!SD.begin(cs_pin)){
Serial.println("Failed!");
return;
}

Serial.println("SD card started.");
Serial.println();

//valida a inicialização
if (!rtc.begin()){
Serial.println("RTC not found!");
while (1); //fica aqui pra sempre
}

// if (!rtc.isrunning()){
// Serial.println("RTC is not working!");
// }

}
/*
Padrao de escrita
saida: umidade(%); temperatura(C); gas(0-1023)

*/
void loop(void)
{
timeout = millis() - start_time;
if (timeout > 10000){
log("gravando dados...\n");
start_time = millis();
}
}

void log(char *msg){
Serial.println("Loggin..");
file = SD.open("vazio.txt", FILE_WRITE);

Serial.println("iniciando leitura de temperatura e humidade");

float h = dht.readHumidity();
float t = dht.readTemperature();
// testa se retorno é valido, caso contrário algo está errado.
if (isnan(t) || isnan(h))
{
Serial.println("Failed to read from DHT");
}
else
{
// file.print("Umidade: ");
file.print(h);
// file.print(" %t");
file.print(";");
// file.print("Temperatura: ");
file.print(t);
// file.print(" *C");
file.print(";");
}
Serial.println("iniciando leitura do sensor de gas");
int valor_analogico = analogRead(pin_a0);
//file.print(" Gas : ");
file.print(valor_analogico);
file.println(";");
Serial.println("gravado");
file.close();

//lcd.setCursor(0, 1);
lcd.begin(16, 2);

// lcd.print("hello, world!");
// lcd.setCursor(0, 1);
// lcd.print("peteca");
Serial.println("U: "+String(h)+" T: "+String(t)+" G: "+String(valor_analogico));
lcd.print("U"+String(int(h))+" T"+String(int(t))+" G"+String(int(valor_analogico/1024)));

// lcd.print("leitura realizada");
delay(500);
Serial.println("Done.");
}

There are multiple libraries with a file named RTClib.h. You need to make sure to use the one your code is written for.

Are you using the Arduino IDE or the Arduino Web Editor?