Option 1 -> lethargically means sluggishly or without energy, which contradicts ensuring perfection.
Option 2 -> abruptly means suddenly or hastily, which doesn't align with careful attention to detail.
Option 3 -> recklessly means carelessly or without caution, the opposite of ensuring perfection.
Option 4 -> meticulously means with careful attention to detail and precision.
Hence, Option 4: meticulously -> The phrase "ensuring that every detail was perfect" directly indicates that Ashu worked with great care and attention to detail, which is exactly what "meticulously" means -> correct