The Code

There were a lot of draft codes, like a lot, which is why these are the finalized code. Who wants to see broken code?

int buzzer = 9;
int co_sensor = 8;
int co_detected;
int msr = 0;
int sensor = A0;
int LED = 4;

#include <LiquidCrystal.h>
LiquidCrystal lcd (12, 11, 5, 4, 3, 2);

#include <dht.h>
dht DHT;
#define DHT11_PIN 7

void setup() {
  int ts = DHT.readTemperature
  int hs = DHT.readHumidity
  lcd.begin(16,2);
  Serial.begin(9600);
  pinMode(4, OUTPUT);
  pinMode(buzzer, OUTPUT);
  pinMode(co_sensor, INPUT);
}

void loop() {
  int chk = DHT.read11(DHT11_PIN);
  lcd.setCursor(0,0);
  lcd.print("Temp-");
  lcd.print(ts);
  lcd.print("c");
  lcd.setCursor(0,1);
  lcd.print("Humidity-");
  lcd.print(hs);
  lcd.print("%");
  Serial.print
  co_detected = digitalRead(co_sensor);
  if(co_detected == LOW) {
    Serial.println("co detected... run for your life!");
    digitalWrite(buzzer, HIGH);
  }
  else {
    Serial.println("no co detected... go eat some pizza");
    digitalWrite(buzzer, LOW);
  }
  msr = analogRead(sensor);
  Serial.println(msr);
  if (msr > 100) {
    Serial.println("soft light");
    digitalWrite(4, LOW);
  }
  else {
    Serial.println("hard light");
    digitalWrite(4, HIGH);
  }
  delay(1000);
}

The Finalized code