Bakit

This question may be answered in at least three different ways, the difference being the degree of formality determined by the context or situation.

Just like pseudo-verbs, interrogative pronouns attract (actor) pronouns so that they always come right after the question word.

bulletKASI
This response is most common in conversations. Here are some examples. The elements in parentheses are usually dropped.
Bakit umalis si Pedro?
Why did Pedro leave?		 (Umalis si Pedro) kasi may klase siya.
(Pedro left) because he has a class.
Bakit walang klase?
Why is there no class?		 (Walang klase) kasi may sakit ang titser.
(There's no class) because the teacher is ill.
Bakit ka pupunta sa Laguna?
Why are you going to Laguna?		 (Pupunta ako sa Laguna) kasi bibisita ako sa lola ko.
(I'm going to Laguna) because I'm going to visit with my grandmother.

 

bulletDAHIL
This is a more formal response, used in both conversational and written form. Here are some examples:
Bakit ka masaya?
Why are you happy?		 (Masaya ako) dahil nandito ka.
(I'm happy) because you're here.
Bakit namatay ang halaman?
Why did the plant die?		 (Namatay ang halaman) dahil hindi ko nadiligan ng dalawang linggo.
(The plant died) because I didn't water it for two weeks.
Bakit tumaas ang presyo ng mga bilihin?
Why did the price of goods go up?		 (Tumaas ang presyo ng mga bilihin) dahil sa krisis sa ekonomiya ng Asya.
(The price of goods went up) because of the economic crisis in Asia.

 

bulletSAPAGKAT
This is the most formal form of response to bakit. It is rarely used in spoken form and is generally associated with literary writing. Here are some examples:
Bakit tayo nagkakamali?
Why do we make mistakes?		 Nagkakamali tayo sapagkat tayo ay tao lamang.
We make mistakes because we're only human.
Bakit umiiyak ang langit?
Why are the heavens crying?		 Umiiyak ang langit sapagkat tuyo na ang lupa.
The heavens are crying because the land has dried up.